Litter to energy: centralized projects versus ‘on-farm’ solutions
The renewable energy and waste to energy sectors are growing rapidly in response to international pressures from Governments to reduce the amount of waste going to landfill sites and to minimize greenhouse gas emissions. As a result, the production of green energy from renewable sources and recycling are becoming increasingly important.
This trend is being reinforced by the increased cost and reduced availability of landfill sites for industrial and other waste. These circumstances provide excellent opportunities to apply gasification technology, particularly where large volumes of biomass and industrial wastes are being generated in areas with relatively high power costs. Under optimum circumstances, the installation of a biomass energy plant can minimize landfill requirements, produce green electricity and process heat and often yield a fertilizer by-product.
Significantly, each of these benefits can be a potential revenue stream to the developer of the project, while the project fundamentally acts as a waste disposal or waste minimization vehicle (Renewable, 2000). Using this approach could be beneficial to the large investor, but another approach could be to look at litter consumption on the farm to produce energy for the individual grower. The overall goals for renewable energy can be achieved; and the grower, who is the major stakeholder and source of litter, would share in the benefits to the industry and environment.
Other sources of renewable energy include wind, solar, hydro, landfill methane and alternative gasification methods, and these will have advantages in specific applications as production of green energy becomes increasingly economic. Given the very large quantities required to meet global governmental targets, it is clear that significant contributions will be required from all alternative sources (Renewable, 2000). However, with the exception of gasification, these other sources (which have yet to be commercially proven) lack the capacity to simultaneously deal with the increasingly important issues of waste disposal and producing useful energy.
Drivers to a cleaner environment
Greenhouse gas emissions
As a result of the greenhouse gas reduction targets set under the 1997 Kyoto Protocol, many governments are under tremendous pressure to reduce emissions (of fossil fuels). Many governments have responded by establishing national targets for the amount of power to be produced from renewable energy sources with lower levels of greenhouse gas emissions. These targets have also brought support for the concept of carbon credits to reward reductions in emissions. International marketing of carbon credits has commenced and once more formal mechanisms are established they will significantly enhance the value of projects that reduce atmospherically harmful emissions (Renewable, 2000).
The US has committed to increasing the use of biomass in the production of electricity. Environmental Protection Agencies throughout the country are increasing the pressure on those industries that create large amounts of waste, and that use environmentally harmful procedures, to find a solution. Emissions trading in Sox and Nox are already a well established and growing market within the US.
The highly developed and densely populated European economies are devoting substantial resources to the reduction of landfill waste and harmful greenhouse gases. The European Union has set ambitious targets to reduce the percentage of biodegradable waste being sent to landfill by 65% within 16 years. On the electricity generation issue, the EU has set a minimum of 12% of total energy produced to be sourced from renewable energy by 2010. Many hundreds of renewable energy installations and facilities will be required to meet this objective. Some estimates predict over $265 billion will be invested in various renewable energy technologies to achieve these ambitious renewable targets by 2010 (Renewable, 2000).
Increasing global concerns about the levels of emissions of greenhouse gases and the culmination of these concerns into international targets for national emission levels in 2010 have resulted in rapidly changing attitudes to a wide range of contributing practices and processes such as coal and oil-fired power stations and gasoline automobiles. It is also now evident that practices such as landfill disposal of biomass waste, surface spreading of untreated animal waste, open burning of combustible waste and low temperature incineration are either under close scrutiny or being phased out, particularly in developed countries and regions. These changes are being achieved through legislative programs, incentives such as green energy premiums and the recent and potentially powerful arrangements for carbon credit trading (Renewable, 2000).
The necessary changes to these practices and processes have resulted in the environment, waste and renewable energy becoming three of the key growth sectors within the global economy.
Importantly, a ‘gasification’ process simultaneously addresses these three issues. The process provides clean saleable energy from biomass waste with very low levels of greenhouse gases. These are attributes that can forge a strong link between environmental responsibility and stakeholder benefit (Renewable, 2000). This is the ‘big picture’ look at the issue, but the solution can be taken to the ‘grass roots’ level.
Thus, converting the poultry litter to energy on the farm and reducing the poultry grower’s dependence on fossil fuels could be the best alternative use for litter. The benefits are potentially enormous to the poultry grower, the integrator and most of all the environment. The independent grower is key to moving the poultry industry into the leadership role and setting the standard for others to follow.
Nutrient management and the poultry industry
Concentrated poultry areas generally produce several times more manure phosphorus (P) than is taken up and removed by crops in these areas. The basic reason for the P imbalance is that large quantities of P are imported into these regions in feedstuffs (grain and inorganic P supplements), resulting in more manure P than is taken up and removed by crops grown in these regions. The surplus P has been building up in soils in concentrated poultry areas for several years, and there is increasing concern about P runoff from these high- P soils causing surface water quality problems. Of greatest concern are ecological issues, and odor and taste problems in drinking water resulting from excess algae growth due to P enrichment of the water. Because of these water quality concerns, restrictions on local land application of poultry litter are likely, and it is projected that alternatives to local land application will be needed for much of the poultry litter produced in concentrated poultry areas.
Combusting or gasifying poultry litter concentrates P, potassium (K), sulfur (S), and micronutrients in the ash, thereby facilitating significantly more economical transport of surplus P out of concentrated poultry areas. Furthermore, the fertilizer value of the nutrient-rich ash is expected to offset most or all of the delivered poultry feedstock costs, resulting in a near net-zero feedstock cost. The forest products industry has demonstrated that using its by-products for energy is economically viable when the delivered feedstock cost is near zero, and this concept should apply to poultry litter.
The ash content of poultry litter is about 15% on an as-received basis. This implies that nutrients such as P, K, S and micronutrients remaining in the ash are 6 to 7-fold more concentrated than in poultry litter. Poultry litter ash has a bulk density about 1.5 to 2.5 times greater than that of poultry litter. The combined effects of greater nutrient concentration and higher bulk density result in nutrient densities 10 to 17 times greater for poultry litter ash than for poultry litter. An order of magnitude increase in nutrient density greatly reduces transportation costs for exporting surplus P from concentrated poultry areas.
In addition to nutrient concentration in the ash and enhanced economics of nutrient transport, combustion and gasification provide a year-round use for poultry litter. This contrasts with land application in which most of the litter is applied in the spring and fall and much of the litter is stored for a significant period of time before being applied on the land. Proper storage is costly. Improper storage results in potential for nutrient and pathogen runoff into surface waters. Because of year-round demand, using poultry litter for energy will facilitate a staggered year-round cleanout of houses, minimize the amount of litter that must be stored, and reduce the potential for nutrient and pathogen runoff from stored litter (Bock, 2000).
The ability for growers to convert poultry litter on farm to ash has a number of key benefits. There are significant reductions in litter volume, storage capacity requirements, truck traffic, shipping and handling cost, land application odor and biosecurity risk, while providing a means to redistribute P onto the land through commercial fertilizers. All of these benefits to the poultry industry are the same for any litter-to-energy project, however taking gasification to the farm could be seen as our best solution yet.
What is gasification?
Most people are very familiar with gasification, but never used the term to describe it. Gasification is considered by many as the cleanest and most efficient combustion method known. It has been used for decades where clean heat is required. Examples include the thousands of vehicles, which were directly fueled by gasifiers (special furnaces design to create syngas) during World War II, or the coal gas ‘works’ which were common in cities all over the world prior to the introduction of natural gas. These produced a gas which combusted so clean it was used in chimney-less household appliances such as cookers and heaters, without adverse effects (Renewable, 2002).
In gasification, biomass is converted to synthesis gas (syngas). Syngas consists largely of carbon monoxide (CO), carbon dioxide (CO2), hydrogen (H2), and complex hydrocarbons (CxHx) and has similarities to natural gas, including most importantly the capacity to burn cleanly. The combination of this process and the very high temperatures achieved (1000°C-1200°C) results in exceptionally clean heat and very low emissions. Gasification technology development continues to make huge gains in the market and larger scale facilities are in the very near future (USDOE, 2002). In the past, the technology was not economical; but today, the efficiency in engineering, design and fabrication has positioned gasification as a viable energy resource. Gasification could be the best technology to convert poultry litter to heat. Gasification operates with low fuel bed temperatures (less than 780°C).
At operating temperatures of about 700°C the waste is broken down into its most basic form – gases – by controlled combustion processes known as pyrolysis and carbon reduction. The remaining noncombustible elements e.g. silica, calcium and metals are extracted as ash, which can be saleable as fertilizer (Renewable, 2002). Given the high ash content of poultry litter (typically 15% by weight), the lower operating temperatures reduces the sintering and clinkering effect (which is common) when litter is exposed to temperatures greater than 800°C. The resultant ash is a by-product rich in phosphorous and potassium, the key inputs to fertilizer.
Potential fuel: poultry manure
“In the USA, each year 8 billion broiler chickens are grown with each chicken producing one kilogram of waste in its average seven-week life.
This equates to approximately 8 million tons per year of chicken litter that is applied to the land. This land application has prompted the local State Agencies to implement a phosphorous based nutrient management plan for most poultry regions” (Murphy, 2000). If all of this litter was diverted to the production of energy and ash for fertilizer, approximately 500 MW of electricity and 1.2 million tons of fertilizer could be produced. Equally important, is the achievement of an environmentally sustainable closed loop system of chicken production. The ultimate analysis of poultry litter (and manure) varies significantly in content among regions, but the typical energy value for litter with 25-28% moisture ranges from 4000–5200 BTU per pound of litter depending on bedding and number of flocks.
Table 1 contains proximate, ultimate and mineral analyses of various ages of litter on the eastern shore of the US (Delmarva region). This fuel would not combust in an average combustor, but can be gasified resulting in a clean heat that can be utilized by the growers.
Litter to energy applications
The applications for poultry litter as a primary fuel source are diverse. Projects are being developed ranging from a 40 MW power station on turkey manure in Minnesota to 120,000 lb/hr steam plant and simple direct drying application in Virginia. Because manures such as poultry litter are collected on a wide scale, the only limiting factor to the size of the project is the availability and the distance the litter is located from the energy production facility.
Economics play an important part in the overall projects ‘bankability’. Should the litter be too far from the site, then the project suffers from high operating costs. The more litter required to sustain the larger projects, the further out a project must go to obtain the litter. Although larger projects are needed and can be made feasible, the ability to capture the needed biomass fuel, particularly litter, increases in risk by the fragmented nature of the litter and the geographical distances.
For example, if a proposed project requires 150,000 t/year of litter in a region where there is approximately 400,000 t/ year land-applied, it can be risky to secure the appropriate fuel quantities, much less make the transportation feasible in obtaining the litter. As the industry knows, the 400,000 t/year of litter is divided up by thousands of independent business people spread out over hundreds of miles. For these reasons alone, centralizing litter will continue to challenge larger projects, thus the ability to reduce this burden on larger projects to solve the surplus issue may be better solved by consuming some litter on the farm, which is faster and more practical. We will explore both large scale and on-farm projects, each proposed to solve the forecast litter surplus, and look at the advantages and disadvantages of each project approach and evaluate their merits.
Large centralized litter to energy projects
The large centralized litter to energy projects usually consist of a centralized heat-raising facility, generally producing steam for a ‘host’ production facility or for the saleable production of electricity, or a combination of both. The poultry litter is collected from the grower and supplied to the facility on a ‘just in time’ basis. The energy production facility depends on the litter broker to collect and supply a specified quality and guaranteed quantity to the plant. Any breaks in the supply chain will result in the energy production facility going offline or having to resort to a backup fuel such as LPG, natural gas or another form of biomass.
Inconsistent litter quality can have grave consequences to the operation of the plant, as litter that is inadvertently supplied too wet can cause major problems to the plant’s thermal output.
Therefore, the claims that these large facilities use large quantities of litter is correct; yet, the collection of fuel of specified quality is the single most important factor in the plant’s economic and operational life. No litter, no output.
Capital investment is more efficiently utilised in large-scale units than in single-farm operations. This economy of scale is hard to challenge, but one should be sensitive to the cost of collecting and transporting the litter that does not exist with the on-farm approach.
The central biomass fueled energy project can bring many benefits to the project host and local community. There are a number of inputs that a project developer can consider. Some of the fuels will generate a small tipping fee that can improve the project economics. Typical project inputs and outputs are in Table 2.
There are a number of small waste streams that can generate tipping fees for the project. For example, in the poultry processing areas there is a large pallet industry. Municipal landfills are charging fees to area companies as high as $45 per ton for wood waste (including pallets). The project could accept clean wood waste at a smaller tipping fee and offset the litter quantity required, help local businesses, reduce landfill volumes, and make money.
The centralized project will generate significant quantities of ash. The ash is high in P and K, key fertilizer inputs, and is transported to area fertilizer producers for further processing. The value of the ash will vary, but a rule of thumb is that the cost of collecting the litter is equal to revenue from the ash. Litter is considered a ‘net zero fuel’.
The litter collection is a very comprehensive logistics challenge. The litter can only be consumed evenly every week in the operating plant, but the litter generation will vary based on the season, grower’s preference, and quantity per house clean-out. These are not the only variables associated with the logistics to be considered but are three major issues that must be addressed. Thus the litter broker becomes as important to a project’s success as the energy host.
High truck traffic is a real community concern. A project looks to centralize the litter movement and increase the density of truck traffic. The community is already sensitive to the amount of trucks common to the poultry industry; and adding 10-20 additional trucks per day can be a huge obstacle to overcome. No matter what type of project is planned; to centralize the litter will require increased truck traffic, thus raising a community issue.
Collection of litter from areas outside the host community can raise the issue of litter movement through the region. Communities are excited about solving the litter problem, but may not be willing to allow large quantities of litter from faraway areas. The project may need to resort to purchasing or competing with farms for litter in the local community, which only drives up the operating cost of the project and tends to defeat the real goal of the project of removing the excess litter from the area. Dealing with the community concerns over the truck traffic and outside litter can pose a real threat to a successful project.
With the volume of litter required, the risk of cross contamination (biosecurity) is increased. The amount of farms (or houses) needed to fulfill the litter demand will require rapid movement between farms. If the steam host is a poultry processing plant, the live grow-out trucks could be inadvertently contaminated by the litter transport process and thus would increase biosecurity issues. Since a centralized litter project has never been accomplished to date, the issue or risk has not been fully evaluated.
A large project is challenged with finding an energy host. Most poultry operations are in remote areas with limited steam users other than the poultry processing facility. A project of this magnitude requires a large steam host (user) or should be close to electricity transmission lines and in a central position for the collection of the litter. Some of the larger projects have required government grants, and(or) subsidies to increase the return on investment for the project developer. In other words, reduce the overall operating cost associated with a central plant or find another alternative project.
’On-farm’ energy is practical
The use of a solid fuel (poultry litter) on the farm is practicable but requires some continued development. Alternative energy for the poultry industry will not be a replacement for fossil fuels, but supplement the fossil fuels by providing over 75% of the poultry house energy requirements. Local heating and backup heating will continue to be provided by propane or natural gas when needed. The type of alternative energies produced can come in the form of hot air, hot water and low pressure steam as economical and effective solutions to reducing the grower’s energy cost.
Typical poultry house
The design and selection of the poultry house have gone through continuous changes and innovations though the years. Today, poultry house design is unique to the integrator preference and experience of what is considered to be best for the business.
The basic poultry house in the US measures approximately 40 ft x 400 ft, which has been found optimum for poultry growth and development.
For the typical poultry house, the heating requirement varies among regions with each equipped with propane (some natural gas) fired forced draft unit heaters to manage the overall temperature requirements. The number of units in a house varies by region and grower/integrator preference. Most poultry houses in Virginia and the Eastern shore can use about 5,000 gallons of propane annually. In areas of North Carolina, growers can use less than 3,000 gallons annually. Thus the heating requirements can vary greatly, and the economic merits will vary directly.
The alternative energy from using poultry litter to heat poultry houses will not replace the propane (natural gas) unit heaters completely, but will provide enough supplemental heat to reduce the need for the gas heaters to operate continually. The goal of the alternative energy ‘on-farm’ design is to reduce a grower’s heating cost by 75% or more. The alternative energy units would be used to maintain an average house temperature of 80-85°F during grow-out by consistently supplying clean heated air into the house 24 hrs/day. The clean heat will be thermostatically controlled and vented to the atmosphere when not required, giving the grower an opportunity to utilize the maximum amount of litter possible.
The fuel would be chicken litter from the growers own operation, which provides a number of benefits. The benefits are not to be considered as finite, but should be viewed as a growing list where the overall merits and secondary benefits from on-farm energy conversion of litter are far reaching:
The technology available can provide clean hot air directly into a house for small farms with 1- 2 houses. For larger farms, hot water generators could be adopted to provide the supplemental heat. Heating of 4 up to 12 houses from a single unit would be extremely cost effective and have a fast payback.
• The goals for retrofits into existing poultry houses should be about a 5-year payback. The payback is directly related to cost of the fossil fuels being used. Propane has varied from $0.75 to $1.35 per gallon in a single year, providing the faster payback potential at $1.35 per gallon. This variability in fuel cost in a single year makes another case for finding a steady renewable fuel that is not sensitive to price changes.
• The conversion of litter to energy on the farm could reduce the energy requirements by 75% annually.
• The on-farm energy may be most effective in new house design where installation cost of propane fired unit heaters can be avoided. This avoided cost would make the on-farm unit more economical and competitive.
• On-farm energy would parallel the day-to-day operation requirements of each farm. • The consumption of chicken litter on the farm reduces the biosecurity risk associated with disease and contamination.
• In using an on-farm solid fuel heater, the heat supplied to the individual house would be clean heat without the combustible gases associated with the propane heating.
• The on-farm unit could be operated 24-hrs/day with excess energy vented to the atmosphere, thus providing the grower a means of waste reduction. The ability to reduce excess litter volume to ash gives the grower a tool to address the issues common with land application of excess litter.
• Use of on-farm technology would reduce the need for state agencies and integrators to fund litter transport programs.
• The ability to convert the litter to useful energy on the farm would be a sound environmental effort and put the growers at the forefront of conservation efforts. Green emission credits could provide some revenue for each grower.
• Ash from the litter consumption can be collected and sold as an input to fertilizer. The ash will be valued on the amount of soluble P and K it contains. Table 1 contains typical mineral analysis of the ash. Expected P solubility could be 50% or greater, giving the ash an approximate value of $35/ton or higher. Given volume reduction and increased bulk density, the ability to store ash is feasible with collection periodically.
• The on-farm heat unit must be robust and fully automatic. Any special or lengthy task to operate the units will reduce the grower’s ability to embrace the technology. However, once adopted, the technology will grow and expand as an industry standard that belongs on the farm.
• Another incentive to move to on-farm energy is the potential surplus litter forecast where some growers could experience an operating cost to dispose of litter. In addition, some state agencies are using litter transport programs to solve the surplus litter dilemma. Consumption on the farm would reduce the need for these costs to the growers and taxpayers.
When one weighs the overall benefits of the on farm program, one can see the initiative is very promising and has enough merits to explore and adopt a strategy.
Concerns about producing on-farm heat
Using on-farm heat production technology is not without concerns or challenges that must be overcome to make the transfer of solid fuel technology to the farm successful. Below are some of the concerns that are apparent.
When the on-farm unit is operating the grower will be required to make periodic inspections and checks. Although once daily is optimal and practical, the unit would add to the grower’s overall daily work load. In addition, the fuel bin would require a refill daily to operate the unit a minimum of 24 hrs. The daily inspection can be viewed as a preventative step to ensure that growers maintain the equipment in top condition, and the incentive would be to keep the propane unit heaters from operating unnecessarily. The cost difference should prove a good incentive to keep the solid fuel units in the best condition to help the growers keep their operating cost at a minimum.
The grower’s ability to understand and utilize the technology will vary significantly, thus the need to make the system simple and robust cannot be overstressed. The technology must be fully automated and contain minimum moving parts. Greater than 10 years would be reasonable target for replacement of any parts.
Additionally, the on farm technology will require preventative maintenance; and each grower addresses maintenance and up-keep differently. It will be important that the technology anticipate lack of maintenance. The equipment supplier should maintain a service agreement with each grower for annual inspection and adjustments. This service agreement should be applied just like a home HVAC service agreement. These agreements would assist growers in keeping their overall operating costs down.
Attitudes vary significantly toward acceptance of change. Some growers view any change as negative or another cost increase that is being passed on by the integrator. Thus, it will be very important to the implementation that the integrators assist with the rapid adoption to gain confidence and acceptance of the growers. Poultry and state agencies must embrace and promote on-farm energy as acceptable and important to survival of the industry.
Grower ability and resources to invest in a new energy plant will vary significantly. With a pay back of five years for some areas, the willingness of growers to embrace the new technology will be slow without an incentive or assistance. Integrators or state agencies could invest in large lots of the equipment to reduce equipment cost through their purchasing power. The industry could make available low cost money or cost sharing programs to adopt the technology over a period of time.
The highest potential for adoption of on-farm heating is during the construction of new houses, where avoided costs can be applied to the new equipment and the payback of investment would be longer. If the new houses are insulated for higher energy efficiencies, then the size of the equipment could be smaller, thus more cost effective than retrofitting older houses. The alternatives are all viable and should be investigated further.
Utilization of poultry litter (or any other animal waste) as a fuel source is gaining acceptance and more technologies are being commercialized. The environmental drivers will continue to force the poultry industry to adopt change to address the litter (manure) environmental issues. By carefully adopting energy projects, removal of litter from land application is possible. The ability to take the solution to the farm itself holds the greatest benefit for the industry.
Bock, B. 2000. Nutrient Management. TVA Public Power Institute.
Murphy, M.L. 2000. Fluidized bed technology solution to animal waste disposal. Energy Products of Idaho.
Renewable Energy Corporation. 2000. Annual Report. Melbourne, Australia. http://www.renrg.com.
Renewable Energy Corporation. 2002. What is gasification? Melbourne, Australia. http://www.renrg.com.
US Department of Energy. 2002. Biofuels. http://www.ott.doe.gov/biofuels/what_are_biofuels. html.