Getting Biofuel from the World’s Garbage

February 24, 2012  |  Comments Off on Getting Biofuel from the World’s Garbage  |  by admin  |  News

There is plenty of garbage on this planet; in fact there is so much garbage that many developed countries are trying to dump their garbage on the lands of lesser developed countries, at a fee of course. But does dumping garbage on other places solve the problem? On the contrary it spreads pollutions and diseases. In fact it is more dangerous to dump garbage in the less developed countries (because there are neither technologies available to process it nor enough awareness). Even creating landfills wastes precious resources.

Rather than having to dump, what if garbage can be used to generate power?

Global Change Biology has published new research that claims replacing gasoline withbiofuel from processed garbage could cut global carbon emissions by 80%. A dream come true, isn’t it?

Great strides are being made in the field of creating biofuels but a galling problem is that the biofuel production causes food shortage. Additionally, farmers are adopting controversial techniques and methods to increase their production and rather than helping the climate, it is harming it.

But garbage is abundantly available, fortunately or unfortunately. Second-generation biofuels like cellulosic ethanol obtained from processed urban waste may the sort of solution that kills two birds with one stone (just an expression, throwing stones at birds and killing them is bad): take care of the garbage and produce fuel.

According to the study author Associate Professor Hugh Tan of the National University of Singapore, “Our results suggest that fuel from processed waste biomass, such as paper and cardboard, is a promising clean energy solution.”

He further says, “If developed fully this biofuel could simultaneously meet part of the world’s energy needs, while also combating carbon emissions and fossil fuel dependency.”

Data from the United Nation’s Human Development Index and the Earth Trendsdatabase was used to arrive at an estimate of how much waste is produced in 173 countries and how much fuel the same countries annually require.

The research team has calculated that 82.93 billion liters of cellulosic ethanol can be produced by the available landfill waste in the world and the resulting biofuel can reduce global carbon emissions in the range of 29.2% to 86.1% for every unit of energy produced.

“If this technology continues to improve and mature these numbers are certain to increase,” concluded co-author Dr. Lian Pin Koh from ETH Zürich. “This could make cellulosic ethanol an important component of our renewable energy future.”

Hydrogen From Waste Materials

February 24, 2012  |  Comments Off on Hydrogen From Waste Materials  |  by admin  |  News

Environmentalists are continuously searching for green and clean fuel. Until now they have been putting a lot of energy and talent into hydrogen fuels because when hydrogen is burned, the only emission it makes is water vapor. So it is a great advantage that burning of hydrogen doesn’t produce carbon dioxide. Clearly, hydrogen is less of a pollutant in the air because it emits little tail pipe pollution. Engineers at the University of Leeds are working on a project keeping hydrogen in mind. They are developing an energy efficient, environmental-friendly hydrogen production system but with a difference. They are trying to extract hydrogen from waste materials. These materials can be vegetable oil or the glycerol by-product of bio-diesel. They are aspiring for the high purity hydrogen-based fuel that could be utilized for large-scale power production. They are also developing hydrogen cells for laptops or other gadgets. A grant of over £400k has been awarded to the University by the Engineering and Physical Sciences Research Council (EPSRC) within a consortium of 12 institutions known as SUPERGEN Sustainable Hydrogen Delivery.

Dr Valerie Dupont from the School of Process, Environmental and Materials Engineering (SPEME) shares his thoughts about future hydrogen fuels: “I can foresee a time when the processes we are investigating could help ensure that hydrogen is a mainstream fuel. We are investigating the feasibility of creating a uniquely energy efficient method of hydrogen production which uses air rather than burners to heat the raw product. Our current research will improve the sustainability of this process and reduce its carbon emissions.”

Hydrogen is largely considered as a clean and green alternative fuel but it is costly to manufacture. If we follow conventional methods of hydrogen production then it emits greenhouse gases. Engineers at the University of Leeds are focusing on these points. The system they are developing is called as Unmixed and Sorption-Enhanced Steam Reforming. They are combining waste products with steam to release hydrogen. This process is comparatively cheaper and cleaner than the existing methods and more energy efficient.

They are using a catalytic reactor for mixing a hydrocarbon-based fuel from plant or waste sources. Waste sources are mixed with steam that produces hydrogen and carbon dioxide and excess water as a byproduct. The water is condensed by cooling without much hassle and the carbon dioxide is removed in situ by a solid sorbent material.

Dr Dupont voices his concern about carbon content: “It’s becoming increasingly necessary for scientists devising new technologies to limit the amount of carbon dioxide they release. This project takes us one step closer to these goals – once we have technologies that enable us to produce hydrogen sustainably, the infrastructure to support its use will grow.”

“We firmly believe that these advanced steam reforming processes have great potential for helping to build the hydrogen economy. Our primary focus now is to ensure the materials we rely on – both to catalyse the desired reaction and to capture the carbon dioxide – can be used over and over again without losing their efficacy.”

Electricity and Desalination from Wastewater

February 15, 2012  |  Comments Off on Electricity and Desalination from Wastewater  |  by admin  |  News

In most part of the world safe and clean drinking water is unavailable for daily consumption and industrial use. Currently to desalinate water two kinds of technologies are being used. First is known as reverse osmosis and the second is electro-dialysis. Both of these processes need huge amount of energy. A team of scientists from China and U.S.A are working to eliminate ninety percent of the salts from seawater or brackish water. They are also trying to generate electricity from wastewater. “Water desalination can be accomplished without electrical energy input or high water pressure by using a source of organic matter as the fuel to desalinate water,” reported in a recent online issue of Environmental Science and Technology.

Bruce Logan, Kappe Professor of Environmental Engineering, Penn State talks about the main highlights of the project, “The big selling point is that it currently takes a lot of electricity to desalinate water and using the microbial desalination cells, we could actually desalinate water and produce electricity while removing organic material from wastewater.”

The team is putting its efforts on a modified a microbial fuel cell for desalinating salty water. Microbial fuel cell is a device that cleverly utilizes naturally occurring bacteria to convert wastewater into clean water and producing electricity in the process.

Currently they are testing the theory and not trying to do something on commercial scale but practical results are quite encouraging for the team. Logan explains the purpose of the whole experiment, “Our main intent was to show that using bacteria we can produce sufficient current to do this. However, it took 200 milliliters of an artificial wastewater — acetic acid in water — to desalinate 3 milliliters of salty water. This is not a practical system yet as it is not optimized, but it is proof of concept.”

A distinctive microbial fuel cell has two chambers. One chamber is filled with wastewater or other nutrients. The second chamber has water. An electrode was inserted in both the chambers. Naturally occurring bacteria becomes active in the wastewater, devours the organic material and generates electricity.

Later on the research team modified the microbial fuel cell by adding a third chamber between the two existing chambers. They also put certain ion specific membranes between the central chamber and the positive and negative electrodes. The ion specific membranes permit either positive or negative ions to pass but not both. Now they place salty water to be desalinated in the central chamber.

About 35 grams of salt per liter is found in seawater and brackish water contains 5 grams per liter. We know that salt dissolves in water and beaks down into positive and negative ions. When the bacteria start consuming the wastewater they also ionize the water. They release charged ions in water known as protons. These protons cannot get through the anion membrane. Therefore the negative ions move from the salty water into the wastewater chamber. What happens at the other electrode? Protons are being consumed so positively charged ions move from the salty water to the other electrode chamber. This way water is desalinated in the middle chamber. The desalination cell discharges ions into the outer chambers. This perks up the efficiency of electricity production compared to microbial fuel cells.

Logan is explaining how to kill two birds with a single stone, “When we try to use microbial fuel cells to generate electricity, the conductivity of the wastewater is very low. If we could add salt it would work better. Rather than just add in salt, however in places where brackish or salt water is already abundant, we could use the process to additionally desalinate salty water, clean the wastewater and dump it and the resulting salt back into the ocean.”

Though this method has some problems we can hope that the research team will tackle those in recent future.

Nanotube Technology Transforms CO2 Into Fuel

January 17, 2012  |  Comments Off on Nanotube Technology Transforms CO2 Into Fuel  |  by admin  |  News

Presence of surplus carbon dioxide in the atmosphere has taken center stage in the environmental science. All over the world people are worried about the excess amount of carbon dioxide in the atmosphere because it’s causing undesirable changes in the surroundings such as green house effect, global warming, melting of ice caps on the glaciers etc. So most of the environmental scientists are trying to minimize the amount of atmospheric carbon dioxide.

Researchers at Pennsylvania State University are working towards the same goal with the help of sunlight and titanium oxide nanotubes. These two elements, sunlight and titanium oxide nanotubes can transform carbon dioxide into methane. Methane can be utilized as energy source. It seems like double benefit. At one hand, we are reducing the quantity of carbon dioxide into the atmosphere and we would be less dependent on fossil fuels.

Craig Grimes of Pennsylvania State University is working on this project with Oomman Varghese, Maggie Paulose and Thomas LaTempa. Craig Grimes shares his views, “Right now there is lots of talk about burying carbon dioxide, which is ridiculous. Instead we can collect the waste out of the smoke stack, put it though a converter, and presto, use sunlight to change [CO2] back into fuel.”

The team of researchers arranged the nanotubes vertically somewhat on the lines of empty honeycomb. The top of the nanotubes is covered with a thin, reddish-brown layer of copper oxide. Here the copper and titanium oxide operate as catalysts. They increase the pace of chemical reactions that happen naturally.

How does the whole process work? When sunlight strikes the copper oxide, carbon dioxide is transformed into carbon monoxide. When sunlight comes into contact with titanium oxide, water molecules split apart. In this reaction hydrogen is freed from the water and the carbon released from CO2 , unite again to create burnable methane. Here oxygen is released as byproduct. If we adjoin more carbon dioxide and sunlight, we will obtain more methane. Craig Grimes calculates that focusing the light collected from 1,100 square feet onto one of the membranes would generate more than 132 gallons of methane on a sunny day. Grimes is of the opinion that formation of methane by this process is the solar power by another name. Instead of storing electrons in batteries, Grimes’ initiative would store energy chemically.

We can use the methane in many ways. In cooking gas cylinders, we can utilize methane instead of propane. Coal-burning power plants could utilize the methane to heat water and generate more electricity. Kyoung-Shin Choi, a chemistry professor at Purdue University, points out another important benefit of the methane. He says we don’t have to invest money in infrastructure as it already exists. “If you want to use hydrogen as a energy source in the future, you have to convert all the existing infrastructure,” said Choi. “But we’ve been using methane for years, and can utilize all the infrastructure we already have.”

“It’s a clean and sustainable cycle as long as you have sun and water,” said Choi.

But we have to wait for its commercial use. Only future can provide an answer to us regarding this.

Trans-America Journey Powered by Waste Vegetable Oil

December 25, 2011  |  Comments Off on Trans-America Journey Powered by Waste Vegetable Oil  |  by admin  |  News

We love to read about different travelers and their adventures, wishing secretly that we could be in their shoes. Here is a young traveler, Stacy Jurich, 2006 graduate of Ohio State University. She is on a 3 ½ month journey across the country, driving her 1981 Mercedes across America. So what is new? She is driving a Mercedes using waste vegetable oil as fuel hence promoting use of alternative fuel. She lives in Toledo, Ohio where she shoulders the responsibility of running a non-profit organization known as “Toledo Choose Local.” This non-profit organization promotes self sustenance using local resources.

Stacy procured her Mercedes online which is equipped as a “grease car”. Any vehicle driven on diesel fuel can use WVO (waste vegetable oil) with a converter kit. The converter kit’s cost ranges from a few hundred to a few thousand dollars. When the winter approaches and temperatures fall, people driving a vehicle on WVO have to buy additional equipment to heat the oil because it can get too thick. The veggie oil that Stacy Jurich is using for her trip, is an environmental friendly fuel because it emits about 25 to 40% less carbon monoxide than regular diesel along with yielding the same, if not better, miles per gallon than diesel.

How does Stacy Jurich acquire her fuel? What she narrates is quite interesting compared to our usual “going to a gas station and filling your tank” routine. She has to use her interpersonal skills as well for refueling purpose. Instead of gas stations she has to spot restaurants! Restaurants dispose off their used vegetable oil in a grease dumpster, and this in turn is picked up by a company that uses the oil for byproducts.

Sometimes the companies themselves are interested in buying back their WVO. In few instances restaurants have to pay the company for the pick-up service. Often engaging restaurateurs into a dialogue and negotiating with them works and they give WVO for free. Stacy also tells about a website called www.fillup4free.com, where one can find people who give away or sell waste vegetable oil.

The collection process can also be an unclean job that takes some considerable time. But the feeling that you are living light on earth and not contributing towards pollution is unbeatable. Jurich wears big leather gloves and a jump suit when she gets oil. She also keeps few containers in her trunk covered in a tarp. Jurich has created a great opportunity for herself for sensitizing people to alternative fuel particularly WVO. She is writing about her 8000 miles journey and her WVO driven vehicle at her website www.vegipowerseesamerica.com

Converting waste into a renewable energy sources

December 24, 2011  |  Comments Off on Converting waste into a renewable energy sources  |  by admin  |  News

Consider a technology that not only keeps your surroundings clean it also produces renewable energy at a low cost. Wheelabrator Technologies Inc., a U.S. pioneer for municipal waste-to-energy technology, wants to make sure that your waste doesn’t go waste. Literally. Wheelabrator’s waste-to-energy facilities produce steam and electricity by burning large quantities of municipal trash and they have been using this proven and time-tested mass-burn technology to produce energy for the past 100 years!

Now this is a company that understood the significance of renewable sources of energy quite a long time ago, back in 1908 and became the first company of its kind to produce the most efficient industrial cleaning and emissions capture technology. They opened their first commercially viable facility in the US in 1975.

There is one thing in this world that we have got in abundance — waste. Large expanses of land are being consumed by mounting heaps of garbage and waste and this waste simply lies there creating tons of pollution and wasting precious land resources. A majority of this garbage is destined to pollute the planet for thousands of years, non-stop. Toxic wastes like glass, processed chemicals, plastics and foams and poisonous gases are perpetually released upon the land and into the air, rivers and seas and they are irreversibly damaging the ecosystem.

Managing municipal waste has always been a huge problem for various US corporations and due to stringent environmental laws in almost all the states it is mandatory that they have a functional and effective waste management plan and this is where Wheelabrator has been helping them by processing almost all types of municipal waste, and wherever possible, turning that waste into renewable energy.

Various waste processing plants have different capacities; for instance if a plant can burn 1500 tonnes of municipal waste per day it has the capacity to generate more than 40,000 kW of renewable electricity that can light up almost 40,000 homes.

Wheelabrator is today one of the leading global innovators helping various gigantic corporations process their waste and turn it into renewable source of energy and electricity. Well-deservedly the company will be celebrating its 100 years of operations this year.

There is another cause for celebration inside the company and that is celebrating the persistent success of employee Artie Cole. His eight patents have made Wheelabrator what it is today. He joined the company 30 years ago as an entry-level maintenance mechanic and currently he is the vice president of the technical services division, proving beyond doubt that innovation and hard work always pays in a company that has its plans well laid out.

There are many ways corporations can dispose of their industrial waste such as using the landfills and incineration but these methods many often don’t work and even if they do they leave behind indelible footprints in the form of highly destructive pollutants whether on the land or in the water. Industrial waste disposal requires careful handling of the poisonous substances and Wheelabrator does it well. And it not only helps corporations deal with their industrial waste it also converts that waste into highly valuable energy source.

Waste as a Renewable Energy Source

November 12, 2011  |  Comments Off on Waste as a Renewable Energy Source  |  by admin  |  News

The enormous increase in the quantum and diversity of waste materials generated by human activity and their potentially harmful effects on the general environment and public health, have led to an increasing awareness about an urgent need to adopt scientific methods for safe disposal of wastes. While there is an obvious need to minimize the generation of wastes and to reuse and recycle them, the technologies for recovery of energy from wastes can play a vital role in mitigating the problems. Besides recovery of substantial energy, these technologies can lead to a substantial reduction in the overall waste quantities requiring final disposal, which can be better managed for safe disposal in a controlled manner while meeting the pollution control standards.

Waste generation rates are affected by socio-economic development, degree of industrialization, and climate. Generally, the greater the economic prosperity and the higher percentage of urban population, the greater the amount of solid waste produced. Reduction in the volume and mass of solid waste is a crucial issue especially in the light of limited availability of final disposal sites in many parts of the world. Although numerous waste and byproduct recovery processes have been introduced, anaerobic digestion has unique and integrative potential, simultaneously acting as a waste treatment and recovery process.

Waste-to-Energy Conversion Pathways

A host of technologies are available for realizing the potential of waste as an energy source, ranging from very simple systems for disposing of dry waste to more complex technologies capable of dealing with large amounts of industrial waste. There are three main pathways for conversion of organic waste material to energy – thermochemical, biochemical and physicochemical.

Thermochemical Conversion
Combustion of waste has been used for many years as a way of reducing waste volume and neutralizing many of the potentially harmful elements within it. Combustion can only be used to create an energy source when heat recovery is included. Heat recovered from the combustion process can then be used to either power turbines for electricity generation or to provide direct space and water heating. Some waste streams are also suitable for fueling a combined heat and power system, although quality and reliability of supply are important factors to consider.

Thermochemical conversion, characterized by higher temperature and conversion rates, is best suited for lower moisture feedstock and is generally less selective for products. Thermochemical conversion includes incineration, pyrolysis and gasification. The incineration technology is the controlled combustion of waste with the recovery of heat to produce steam which in turn produces power through steam turbines. Pyrolysis and gasification represent refined thermal treatment methods as alternatives to incineration and are characterized by the transformation of the waste into product gas as energy carrier for later combustion in, for example, a boiler or a gas engine.

Biochemical Conversion
The bio-chemical conversion processes, which include anaerobic digestion and fermentation, are preferred for wastes having high percentage of organic biodegradable (putrescible) matter and high moisture content. Anaerobic digestion is a reliable technology for the treatment of wet, organic waste. Organic waste from various sources is composted in highly controlled, oxygen-free conditions circumstances resulting in the production of biogas which can be used to produce both electricity and heat. Anaerobic digestion also results in a dry residue called digestate which can be used as a soil conditioner.

Alcohol fermentation is the transformation of organic fraction of biomass to ethanol by a series of biochemical reactions using specialized microorganisms. It finds good deal of application in the transformation of woody biomass into cellulosic ethanol.

Physico-chemical Conversion
The physico-chemical technology involves various processes to improve physical and chemical properties of solid waste. The combustible fraction of the waste is converted into high-energy fuel pellets which may be used in steam generation. Fuel pellets have several distinct advantages over coal and wood because it is cleaner, free from incombustibles, has lower ash and moisture contents, is of uniform size, cost-effective, and eco-friendly.

Factors affecting Energy Recovery from waste
The two main factors which determine the potential of recovery of energy from wastes are the quantity and quality (physico-chemical characteristics) of the waste. Some of the important physico-chemical parameters requiring consideration include:

  • Size of constituents
  • Density
  • Moisture content
  • Volatile solids / Organic matter
  • Fixed carbon
  • Total inerts
  • Calorific value

Often, an analysis of waste to determine the proportion of carbon, hydrogen, oxygen, nitrogen and sulfur (ultimate analysis) is done to make mass balance calculations, for both thermochemical and biochemical processes. In case of anaerobic digestion, the parameters C/N ratio (a measure of nutrient concentration available for bacterial growth) and toxicity (representing the presence of hazardous materials which inhibit bacterial growth), also require consideration.

Significance of Waste-to- Energy (WTE) Plants
While some still confuse modern waste-to-energy plants with incinerators of the past, the environmental performance of the industry is beyond reproach. Studies have shown that communities that employ waste-to-energy technology have higher recycling rates than communities that do not utilize waste-to-energy. The recovery of ferrous and non-ferrous metals from waste-to-energy plants for recycling is strong and growing each year. In addition, numerous studies have determined that waste-to-energy plants actually reduce the amount of greenhouse gases that enter the atmosphere.

Nowadays, waste-to-energy plants based on combustion technologies are highly efficient power plants that utilize municipal solid waste as their fuel rather than coal, oil or natural gas. Far better than expending energy to explore, recover, process and transport the fuel from some distant source, waste-to-energy plants find value in what others consider garbage. Waste-to-energy plants recover the thermal energy contained in the trash in highly efficient boilers that generate steam that can then be sold directly to industrial customers, or used on-site to drive turbines for electricity production. WTE plants are highly efficient in harnessing the untapped energy potential of organic waste by converting the biodegradable fraction of the waste into high calorific value gases like methane. The digested portion of the waste is highly rich in nutrients and is widely used as biofertilizer in many parts of the world.

Waste-to-Energy around the World
To an even greater extent than in the United States, waste-to-energy has thrived in Europe and Asia as the preeminent method of waste disposal. Lauding waste-to-energy for its ability to reduce the volume of waste in an environmentally-friendly manner, generate valuable energy, and reduce greenhouse gas emissions, European nations rely on waste-to-energy as the preferred method of waste disposal. In fact, the European Union has issued a legally binding requirement for its member States to limit the landfilling of biodegradable waste.

According to the Confederation of European Waste-to-Energy Plants (CEWEP), Europe currently treats 50 million ton of wastes at waste-to-energy plants each year, generating an amount of energy that can supply electricity for 27 million people or heat for 13 million people. Upcoming changes to EU legislation will have a profound impact on how much further the technology will help achieve environmental protection goals.

A Glance at Feedstock for Waste-to-Energy Plants

Agricultural Residues
Large quantities of crop residues are produced annually worldwide, and are vastly underutilised. The most common agricultural residue is the rice husk, which makes up 25% of rice by mass. Other residues include sugar cane fibre (known as bagasse), coconut husks and shells, groundnut shells, cereal straw etc. Current farming practice is usually to plough these residues back into the soil, or they are burnt, left to decompose, or grazed by cattle. A number of agricultural and biomass studies, however, have concluded that it may be appropriate to remove and utilise a portion of crop residue for energy production, providing large volumes of low cost material. These residues could be processed into liquid fuels or combusted/gasified to produce electricity and heat.

Animal Waste
There are a wide range of animal wastes that can be used as sources of biomass energy. The most common sources are animal and poultry manures. In the past this waste was recovered and sold as a fertilizer or simply spread onto agricultural land, but the introduction of tighter environmental controls on odour and water pollution means that some form of waste management is now required, which provides further incentives for waste-to-energy conversion. The most attractive method of converting these waste materials to useful form is anaerobic digestion which gives biogas that can be used as a fuel for internal combustion engines, to generate electricity from small gas turbines, burnt directly for cooking, or for space and water heating. Food processing and abattoir wastes are also a potential anaerobic digestion feedstock.

Sugar Industry Wastes
The sugar cane industry produces large volumes of bagasse each year. Bagasse is potentially a major source of biomass energy as it can be used as boiler feedstock to generate steam for process heat and electricity production. Most sugar cane mills utilise bagasse to produce electricity for their own needs but some sugar mills are able to export substantial amount of electricity to the grid.

Forestry Residues
Forestry residues are generated by operations such as thinning of plantations, clearing for logging roads, extracting stem-wood for pulp and timber, and natural attrition. Wood processing also generates significant volumes of residues usually in the form of sawdust, off-cuts, bark and woodchip rejects. This waste material is often not utilized and often left to rot on site. However it can be collected and used in a biomass gasifier to produce hot gases for generating steam.

Industrial Wastes
The food industry produces a large number of residues and by-products that can be used as biomass energy sources. These waste materials are generated from all sectors of the food industry with everything from meat production to confectionery producing waste that can be utilised as an energy source. Solid wastes include peelings and scraps from fruit and vegetables, food that does not meet quality control standards, pulp and fibre from sugar and starch extraction, filter sludges and coffee grounds. These wastes are usually disposed of in landfill dumps.

Liquid wastes are generated by washing meat, fruit and vegetables, blanching fruit and vegetables, pre-cooking meats, poultry and fish, cleaning and processing operations as well as wine making. These waste waters contain sugars, starches and other dissolved and solid organic matter. The potential exists for these industrial wastes to be anaerobically digested to produce biogas, or fermented to produce ethanol, and several commercial examples of waste-to-energy conversion already exist.

Municipal Solid Waste (MSW)
Millions of tonnes of household waste are collected each year with the vast majority disposed of in landfill dumps. The biomass resource in MSW comprises the putrescibles, paper and plastic and averages 80% of the total MSW collected. Municipal solid waste can be converted into energy by direct combustion, or by natural anaerobic digestion in the landfill. At the landfill sites the gas produced by the natural decomposition of MSW (approximately 50% methane and 50% carbon dioxide) is collected from the stored material and scrubbed and cleaned before feeding into internal combustion engines or gas turbines to generate heat and power. The organic fraction of MSW can be anaerobically stabilized in a high-rate digester to obtain biogas for electricity or steam generation.

Sewage
Sewage is a source of biomass energy that is very similar to the other animal wastes. Energy can be extracted from sewage using anaerobic digestion to produce biogas. The sewage sludge that remains can be incinerated or undergo pyrolysis to produce more biogas.

Black Liquor
Pulp and Paper Industry is considered to be one of the highly polluting industries and consumes large amount of energy and water in various unit operations. The wastewater discharged by this industry is highly heterogeneous as it contains compounds from wood or other raw materials, processed chemicals as well as compound formed during processing. Black liquor can be judiciously utilized for production of biogas using anaerobic UASB technology.

Conclusions

Waste-to-energy plants offer two important benefits of environmentally safe waste management and disposal, as well as the generation of clean electric power. Waste-to-energy facilities produce clean, renewable energy through thermochemical, biochemical and physicochemical methods. The growing use of waste-to-energy as a method to dispose off solid and liquid wastes and generate power has greatly reduced environmental impacts of municipal solid waste management, including emissions of greenhouse gases. Waste-to-energy conversion reduces greenhouse gas emissions in two ways. Electricity is generated which reduces the dependence on electrical production from power plants based on fossil fuels. The greenhouse gas emissions are significantly reduced by preventing methane emissions from landfills. Moreover, waste-to-energy plants are highly efficient in harnessing the untapped sources of energy from a variety of wastes.

An environmentally sound and techno-economically viable methodology to treat biodegradable waste is highly crucial for the sustainability of modern societies. A transition from conventional energy systems to one based on renewable resources is necessary to meet the ever-increasing demand for energy and to address environmental concerns.

Negative Impacts of Incineration-based Waste-to-Energy Technology

October 24, 2011  |  Comments Off on Negative Impacts of Incineration-based Waste-to-Energy Technology  |  by admin  |  News

Despite being an attractive technological option for waste management, combustion-based processes for municipal solid waste (MSW) treatment are a subject of intense debate around the world. In the absence of effective controls, harmful pollutants may be emitted into the air, land and water which may influence human health and environment. Although incineration of municipal waste coupled with energy recovery can form an essential part of an integrated waste management system, yet strict controls are required to prevent its negative impacts on human health and environment.

Incineration technology is the controlled combustion of waste with the recovery of heat to produce steam that in turn produces power through steam turbines. MSW after pretreatment is fed to the boiler of suitable choice wherein high pressure steam is used to produce power through a steam turbine. Pyrolysis is extensively used in the petrochemical industry and can be applied to municipal waste treatment where organic waste is transformed into combustible gas and residues. Gasification is another alternative which normally operates at a higher temperature than pyrolysis in limited quantity of air. While both pyrolysis and gasification are feasible technologies to handle municipal waste, commercial applications of either technology have been limited.

Incineration-based technologies have been a subject of intense debate in the environmental, social and political circles. This article evaluates incineration on the basis of three parameters – environmental, human health and economic impact – and proposes an integrated mechanism to maintain a fine balance between energy recovery and environmental concerns.

Environmental Issues
The incineration process produces two types of ash. Bottom ash comes from the furnace and is mixed with slag, while fly ash comes from the stack and contains components that are more hazardous. In municipal waste incinerators, bottom ash is approximately 10% by volume and approximately 20 to 35% by weight of the solid waste input. Fly ash quantities are much lower, generally only a few percent of input. Emissions from incinerators can include heavy metals, dioxins and furans, which may be present in the waste gases, water or ash. Plastic and metals are the major source of the calorific value of the waste. The combustion of plastics, like polyvinyl chloride (PVC) gives rise to these highly toxic pollutants.

Toxics are created at various stages of such thermal technologies, and not only at the end of the stack. These can be created during the process, in the stack pipes, as residues in ash, scrubber water and filters, and in fact even in air plumes which leave the stack. There are no safe ways of avoiding their production or destroying them, and at best they can be trapped at extreme cost in sophisticated filters or in the ash. The ultimate release is unavoidable, and if trapped in ash or filters, these become hazardous wastes themselves.

The pollutants which are created, even if trapped, reside in filters and ash, which need special landfills for disposal. In case energy recovery is attempted, it requires heat exchangers which operate at temperatures which maximize dioxin production. If the gases are quenched, it goes against energy recovery. Such projects disperse incinerator ash throughout the environment which subsequently enter our food chain.

Incinerator technological intervention in the waste stream distorts waste management. Such systems rely on minimum guaranteed waste flows. It indirectly promotes continued waste generation while hindering waste prevention, reuse, composting, recycling, and recycling-based community economic development. It costs cities and municipalities more and provides fewer jobs than comprehensive recycling and composting and also hinders the development of local recycling-based businesses.

Human Health Concerns
Waste incineration systems produce a wide variety of pollutants which are detrimental to human health. Such systems are expensive and does not eliminate or adequately control the toxic emissions from chemically complex MSW. Even new incinerators release toxic metals, dioxins, and acid gases. Far from eliminating the need for a landfill, waste incinerator systems produce toxic ash and other residues.

The waste-to-energy program to maximize energy recovery is technologically incompatible with reducing dioxins emissions. Dioxins are the most lethal Persistent Organic Pollutants (POPs) which have irreparable environmental health consequences. The affected populace includes those living near the incinerator as well as those living in the broader region. People are exposed to toxics compounds in several ways:

* By breathing the air which affects both workers in the plant and people who live nearby;
* By eating locally produced foods or water that have been contaminated by air pollutants from the incinerator; and
* By eating fish or wildlife that have been contaminated by the air emissions.

Dioxin is a highly toxic compound which may cause cancer and neurological damage, and disrupt reproductive systems, thyroid systems, respiratory systems etc.

Financial Impacts
All over the developed world, almost half the investment is put in control systems to reduce toxic emissions such as mercury, cadmium, lead, dioxins, furans, volatile organic compounds etc. For example a 2000 MT per day incinerator can cost upwards of $500 million in Europe, half of the cost being put into emission control. Another problem arises in the case of developing countries because the average calorific value garbage in such countries is about 800 cal / kg. For combustion technologies to succeed they would need about 2000 to 3000 cal / kg, other wise auxiliary fuel has to be added. This makes the process more uneconomical and polluting than it already is.

Most of the size and expense of the incinerator is dedicated to the pollution control equipment. The first component of the pollution control equipment is the stage at which ammonia is injected into the gases produced from the burning process which assists in the removal of NOx. The removal of mercury is achieved by the injection of activated carbon. Lime is then injected in the dry scrubber stage whereby the acid gases are removed. Further, most incinerators have a bag-house or electrostatic precipitator to facilitate the capture of particulate and toxics. Thus, it can be realized that the cost of the pollution control system over-rides the cost of the incinerator by a huge margin.

Incineration experts generally state that to have an economically viable operation, it is required to have an incinerator that burns at least 1000 tonnes of garbage each day. The cost to build such a facility is approximately $100 million. Operating costs to maintain the equipment, especially the pollution control equipment is also high.

It is dangerous to bury fly ash in a regular municipal landfill. A special hazardous waste landfill is required which is almost ten times costlier than a municipal landfill. Therefore, the cost of municipal waste incineration shoots up due to the requirement of a special landfill for fly ash disposal.

Conclusions
The adoption of alternative cleaner methods for the disposal of municipal garbage is necessary. According to the United Nations Environment Programme (UNEP), incinerators are the leading source of dioxin into the global environment. The EPA, in a recent study, identified dioxins as the cause of many cancers, the worst component being TCDD (also known as Agent Orange).

The need for low-cost solutions presents significant difficulties, but it is not an impossible task. The ideal resource management strategy for MSW is to avoid its generation in the first place. In 1993, a Royal Commission on Environmental Pollution in England issued a four-stage decision procedure of which the first two stages state:

* Wherever possible, avoid creating wastes,
* Where wastes are unavoidable, recycle them if possible.

This implies changing production and consumption patterns to eliminate the use of disposable, non-reusable, non-returnable products and packaging.

An integrated solid waste management (ISWM) is essential to establish a waste hierarchy to identify the key elements. The general hierarchy should be comprised of the following order:

1. Reduce
2. Reuse
3. Recycle
4. Waste minimization and recovery of energy from waste by composting, anaerobic digestion, incineration etc.
5. Landfilling

The cost of building and operating incinerators or providing special landfill sites is enormous. If substantial parts of these funds were to be diverted towards waste minimisation and encouraging recycling, the need for waste disposal could be enormously reduced, apart from reducing the dangers which arise from both incineration and landfill. It is essential to explore the potential of environment-friendly technologies, like anaerobic digestion (AD), for the treatment of municipal waste because it holds the promise to address two highly important environmental concerns – waste management and renewable energy.

Anaerobic Digestion of Biomass

September 26, 2011  |  Comments Off on Anaerobic Digestion of Biomass  |  by admin  |  News

The generation and disposal of organic waste without adequate treatment result in significant environmental pollution. Besides health concerns for the people in the vicinity of disposal sites, degradation of waste leads to uncontrolled release of greenhouse gases (GHGs) into the atmosphere. Conventional means, like aeration, is energy intensive, expensive and also generates a significant quantity of biological sludge. In this context, anaerobic digestion offers potential energy savings and is a more stable process for medium and high strength organic effluents. Waste-to-Energy (WTE) plants, based on anaerobic digestion of biomass, are highly efficient in harnessing the untapped renewable energy potential of organic waste by converting the biodegradable fraction of the waste into high calorific gases. Apart from treating the wastewater, the methane produced from the biogas facilities can be recovered, with relative ease, for electricity generation and industrial/domestic heating.

An Attractive Option for Renewable Power

Anaerobic digestion plants not only decrease GHGs emission but also reduce dependence on fossil fuels for energy requirements. The anaerobic process has several advantages over other methods of waste treatment. Most significantly, it is able to accommodate relatively high rates of organic loading. With increasing use of anaerobic technology for treating various process streams, it is expected that industries would become more economically competitive because of their more judicious use of natural resources. Therefore, anaerobic digestion technology is almost certainly assured of increased usage in the future.

Benefits of Anaerobic Digestion

Anaerobic digestion provides a variety of benefits. These may be classified into three groups viz. environmental, economic and energy benefits:

The environmental benefits include:
1. Elimination of malodorous compounds.
2. Reduction of pathogens.
3. Deactivation of weed seeds.
4. Production of sanitized compost.
5. Decrease in GHGs emission.
6. Reduced dependence on inorganic fertilizers by capture and reuse of nutrients.
7. Promotion of carbon sequestration
8. Beneficial reuse of recycled water
9. Protection of groundwater and surface water resources.
10. Improved social acceptance

Anaerobic digestion is advantageous in terms of energy in the following manner:
1. Anaerobic digestion is a net energy-producing process.
2. A biogas facility generates high-quality renewable fuel.
3. Surplus energy as electricity and heat is produced during anaerobic digestion of biomass.
4. Anaerobic digestion reduces reliance on energy imports.
5. Such a facility contributes to decentralized, distributed power systems.
6. Biogas is a rich source of electricity, heat, and transportation fuel.

The economic benefits associated with a biomass-to-biogas facility are:
1. Anaerobic digestion transforms waste liabilities into new profit centers.
2. The time devoted to moving, handling and processing manure is minimized.
3. Anaerobic digestion adds value to negative value feedstock.
4. Income can be obtained from the processing of waste (tipping fees), sale of organic fertilizer, carbon credits and sale of power.
5. Power tax credits may be obtained from each kWh of power produced.
6. A biomass-to-biogas facility reduces water consumption.
7. It reduces dependence on energy imports.
8. Anaerobic digestion plants increases self-sufficiency.

Feedstock for Anaerobic Digestion Plants

A wide range of feedstock is available for anaerobic digesters. In addition to MSW, large quantity of waste, in both solid and liquid forms, is generated by the industrial sector like breweries, sugar mills, distilleries, food-processing industries, tanneries, and paper and pulp industries. Out of the total pollution contributed by industrial sub-sectors, nearly 40% of the total organic pollution is contributed by the food products industry alone. Food products and agro-based industries together contribute 65% to 70% of the total industrial wastewater in terms of organic load. Poultry waste has the highest per tonne energy potential of electricity per tonne but livestock have the greatest potential for energy generation in the agricultural sector.

Most small-scale units such as tanneries, textile bleaching and dying, dairy, slaughterhouses cannot afford effluent treatment plants of their own because of economies of scale in pollution abatement. Recycling/recovery/re-use of products from the wastes of such small-scale units by adopting suitable technology could be a viable proposition. Generation of energy using anaerobic digestion process has proved to be economically attractive in many such cases. The urban municipal waste (both solid and liquid) – industrial waste coming from dairies, distilleries, pressmud, tanneries, pulp and paper, and food processing industries, etc., agro-waste and biomass in different forms – if treated properly, has a tremendous potential for energy generation. Fig 1 lists the possible feedstock for waste-to-energy plants based on anaerobic digestion of biomass.

Agricultural Origin

  • Livestock manure
  • Agricultural residues
  • Animal mortalities
  • Energy crops

Industrial Origin

  • Wastewater
  • Industrial sludges
  • Industrial by-products
  • Slaughterhouse waste
  • Spent beverages
  • Biosolids

Municipal Origin

  • Sewage sludge
  • Municipal solid waste
  • Food residuals

Anaerobic Digestion of Livestock Manure

The livestock industry is an important contributor to the economy of any country. More than one billion tons of manure is produced annually by livestock in the United States. Animal manure is a valuable source of nutrients and renewable energy. However, most of the manure is collected in lagoons or left to decompose in the open which pose a significant environmental hazard. The air pollutants emitted from manure include methane, nitrous oxide, ammonia, hydrogen sulfide, volatile organic compounds and particulate matter, which can cause serious environmental concerns and health problems.

Anaerobic digestion is a unique treatment solution for animal agriculture as it can deliver positive benefits related to multiple issues, including renewable energy, water pollution, and air emissions. Anaerobic digestion of animal manure is gaining popularity as a means to protect the environment and to recycle materials efficiently into the farming systems. Waste-to-Energy (WTE) plants, based on anaerobic digestion of biomass, are highly efficient in harnessing the untapped renewable energy potential of organic waste by converting the biodegradable fraction of the waste into high calorific gases.

Potential biogas yield from various animals
Animal – Biogas Yield/Ton Manure (ft3/ton/day)

  • Dairy – 920
  • Beef – 1148
  • Swine – 741
  • Poultry – 2266

The establishment of anaerobic digestion systems for livestock manure stabilization and energy production has accelerated substantially in the past several years. There are more than 111 digesters operating at commercial livestock facilities in the United States which generated around 215 million kWh equivalent of useable energy. Besides generating electricity (170 million kWh), biogas is used as boiler and domestic fuel. Many of the projects that generate electricity also capture waste heat for various in-house requirements.

In the past, livestock waste was recovered and sold as a fertilizer or simply spread onto agricultural land. The introduction of tighter environmental controls on odor and water pollution means that some form of waste management is necessary, which provides further incentives for biomass-to-energy conversion.

Important Factors to Consider

The main factors that influence biogas production from livestock manure are pH and temperature of the feedstock. It is well established that a biogas plant works optimally at neutral pH level and mesophilic temperature of around 35o C. Carbon-nitrogen ratio of the feed material is also an important factor and should be in the range of 20:1 to 30:1. Animal manure has a carbon – nitrogen ratio of 25:1 and is considered ideal for maximum gas production. Solid concentration in the feed material is also crucial to ensure sufficient gas production, as well as easy mixing and handling. Hydraulic retention time (HRT) is the most important factor in determining the volume of the digester which in turn determines the cost of the plant; the larger the retention period, higher the construction cost.

An emerging technological advance in anaerobic digestion that may lead to increased biogas yields is the use of ultrasound to increase volatile solids conversion. This process disintegrates solids in the influent, which increases surface area and, in turn, allows for efficient digestion of biodegradable waste.

Process Description of WTE Facility Based on Livestock Manure

The layout of a typical biogas facility using livestock manure as raw material is shown in Fig 3. The fresh animal manure is stored in a collection tank before its processing to the homogenization tank which is equipped with a mixer to facilitate homogenization of the waste stream. The uniformly mixed waste is passed through a macerator to obtain uniform particle size of 5-10 mm and pumped into suitable-capacity anaerobic digesters where stabilization of organic waste takes place.

In anaerobic digestion, organic material is converted to biogas by a series of bacteria groups into methane and carbon dioxide. The majority of commercially operating digesters are plug flow and complete-mix reactors operating at mesophilic temperatures. The type of digester used varies with the consistency and solids content of the feedstock, with capital investment factors and with the primary purpose of digestion.

Biogas contain significant amount of hydrogen sulfide (H2S) gas which needs to be stripped off due to its highly corrosive nature. The removal of H2S takes place in a biological desulphurization unit in which a limited quantity of air is added to biogas in the presence of specialized aerobic bacteria which oxidizes H2S into elemental sulfur.

Gas is dried and vented into a CHP unit to a generator to produce electricity and heat. The size of the CHP system depends on the amount of biogas produced daily. The digested substrate is passed through screw presses for de-watering and then subjected to solar drying and conditioning to give high-quality organic fertilizer. The press water is treated in an effluent treatment plant based on activated sludge process which consists of an aeration tank and a secondary clarifier. The treated wastewater is recycled to meet in-house plant requirements. A chemical laboratory is necessary to continuously monitor important environmental parameters such as BOD, COD, VFA, pH, ammonia, C:N ratio at different locations for efficient and proper functioning of the process.

The continuous monitoring of the biogas plant is achieved by using a remote control system such as Supervisory Control and Data Acquisition (SCADA) system. This remote system facilitates immediate feedback and adjustment, which can result in energy savings.

Utilization of Biogas and Digestate

An anaerobic digestion plant produces two outputs, biogas and digestate, both can be further processed or utilised to produce secondary outputs. Biogas can be used for producing electricity and heat, as a natural gas substitute and also a transportation fuel. A combined heat and power plant system (CHP) not only generates power but also produces heat for in-house requirements to maintain desired temperature level in the digester during cold season. CHP systems cover a range of technologies but indicative energy outputs per m3 of biogas are approximately 1.7 kWh electricity and 2.5kWh heat. The combined production of electricity and heat is highly desirable because it displaces non-renewable energy demand elsewhere and therefore reduces the amount of carbon dioxide released into the atmosphere.

In Sweden, the compressed biogas is used as a transportation fuel for cars and buses. Biogas can also be upgraded and used in gas supply networks. The use of biogas in solid oxide fuel cells is being researched.

The surplus heat energy generated may be utilized through a district heating network. Thus, there is potential scope for biogas facilities in the proximity of new housing and development areas, particularly if the waste management system could utilise kitchen and green waste from the housing as a supplement to other feed stock.

Digestate can be further processed to produce liquor and a fibrous material. The fiber, which can be processed into compost, is a bulky material with low levels of nutrients and can be used as a soil conditioner or a low level fertilizer. A high proportion of the nutrients remain in the liquor, which can be used as a liquid fertilizer.

Conclusions

Anaerobic digestion of biomass offer two important benefits of environmentally safe waste management and disposal, as well as the generation of clean electric power. The growing use of digestion technology as a method to dispose off livestock manure has greatly reduced its environmental and economic impacts. Biomass-to-biogas transformation mitigates GHGs emission and harness the untapped potential of a variety of organic waste. Anaerobic digestion technology affords greater water quality benefits than standard slurry storage due to lower pollution potential. It also provides additional benefits in terms of meeting the targets under the Kyoto Protocol and other environmental legislations.

The livestock industry is a vitally important contributor to the economy of any country, regardless of the degree of industrialization. Animal manure is a valuable source of renewable energy; additionally, it has soil enhancement properties. Anaerobic digestion is a unique treatment solution for animal agriculture as it can deliver positive benefits related to multiple issues, including renewable energy, water pollution, and air emissions. Anaerobic digestion of animal manure is gaining popularity as a means to protect the environment and to produce clean energy. There is an urgent need to integrate the digester with manure management systems for effective implementation of the anaerobic digestion technology to address associated environmental concerns and to harness renewable energy potential of livestock.

Turning Airborne Carbon Into Fuel

August 28, 2011  |  Comments Off on Turning Airborne Carbon Into Fuel  |  by admin  |  News

We are already experiencing the ill effects of greenhouse gases in the form of global warming, glaciers and polar ice melting, rise in the sea level and sudden, unpredictable variation in weather, turning catastrophic sometimes. The eventual effect of global warming is sending a chill down the spines of environmentalists. Several teams of researchers are working overnight on carbon capture technology. It intends to remove undesirable amount of carbon dioxide, the main culprit in global warming, from the atmosphere.

Carbon Capture

Scientists are working on erecting towers which will work as giant trees with immense appetite for carbon. These giant tower trees can absorb carbon from automobiles, forest fires, volcanic eruptions, deforested areas, burning oil wells, agricultural and industrial burning etc. The capacity of these towers for carbon absorption will be one ton a day, per tower.

A tree absorbs the same amount of carbon in a century. At the same time a tree emits carbon dioxide during metabolic activities or while rotting. But these towers will not do the same. The captured carbon can be stored underground for industrial purposes. For example, stored carbon can be reprocessed into liquid form. This liquid carbon can be used for motor fuel.

Global Research Technologies, LLC (GRT), is continuing to refine ACCESS(TM), its air-capture technology product named for the initials in the phrase “Atmospheric Carbon CapturE SystemS”.

GRT is a research and development company dedicated to the commercialization of products and processes with a positive energy and environmental impact.

GRT’s proof-of-concept successes have established that the firm is on its way to designing and building patented air-capture technology that will eventually enable the removal of millions of tons of CO2 a day from the earth’s atmosphere. GRT is also refining its long-term business model and working to integrate large numbers of future ACCESS units into markets that produce and use CO2.

Apart from sucking carbon from the atmosphere another advantage of ACCESS units is that they can be established anywhere with little effort. For instance they can be placed at locations replete with carbon emission. Both big and small versions of access are going to be available in a few years.