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A research paper of the potential use of livestock waste as an alternative use fuel for sustainable agriculture.
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Biogas In AgricultureThe Potential for Livestock Waste to Act as an Alternative Source of Energy
Jason Boothe
GEOG 317, Fall 2010Dr. TashDecember 9, 2010
Biogas In Agriculture i
Table of Contents
Introduction.........................................................................................................1What is Biogas? How is it produced?...................................................................1Uses of Biogas.....................................................................................................2Benefits of Using Biogas......................................................................................3
Environmental..............................................................................................................3Energy.........................................................................................................................4Economics....................................................................................................................5
Drawbacks of Biogas Usage.................................................................................6Environmental..............................................................................................................6Energy.........................................................................................................................7Economics....................................................................................................................7
Conclusion...........................................................................................................8
Biogas In Agriculture iii
Introduction.As movements continue towards green and sustainable ways to use
and harness energy, the agriculture sector has been looking at ways to
become more green and sustainable. For agriculture these movements
have been examining ways to decrease the usage of fossil fuels but
limiting the passing on of energy cost to the consumer of their products
when using alternative energy sources. One possible alternative energy
source being investigated is that of biogas. In agriculture, the usage of
biogas is would be mostly constricted in the livestock area, where there is
adequate raw materials produced for biogas production. However the
question remains, in the agricultural sector of North America, is biogas
usage and production on-site an cost-effective alternative to fossil fuel
use, and does it’s use allow for a more sustainable, “green”, and
environmentally conscious agriculture sector.
What is Biogas? How is it produced?Biogas is a
combustible mixture
of gases produced
by micro-organisms
when livestock
manure and other
biological wastes
are allowed to
Biogas In Agriculture 1
Figure 1. Diagram showing biogas production and storage. (German) Source: connect.in.com
ferment in the absence of air in closed containers. The major constituents
of biogas are methane (CH4, 60 percent or more by volume) and carbon
dioxide (CO2, about 35 percent); but small amounts of water vapor,
hydrogen sulphide (H2S), carbon monoxide (CO), and nitrogen (N2) are
also present (Kangmin, 2006)
The composition of biogas varies according to the biological
material. The methane content of biogas produced from night soil (human
excreta), chicken manure and wastewater from slaughterhouse
sometimes could reach 70 percent or more, while that from stalk and
straw of crops is about 55 percent. The concentration of H2S in biogas
produced from chicken manure and molasses could be as high as 4
000mg/m3, and from alcohol wastewater even higher at 10 000 mg/m3
(Kangmin, 2006)
While the natural break down of these waste products produces
biogas, for its efficient use a fuel source, a bioreactor system is
recommended. The bioreactor breaks down the waste material in a more
controlled environment then allowing it to break down naturally, for a
more efficient process. These bioreactors range in size and type,
dependent on the amount of raw material need to be broken down and
the composition of the raw material.
Uses of Biogas.Biogas is mainly used as fuel, like natural gas, while the digested
mixture of liquids and solids, the so called ‘bio-slurry’ and ‘bio-sludge’,
are mainly used as organic fertilizer for crops.
Biogas In Agriculture 2
Biogas can be used directly for cooking and for co-generation of
electricity and heat, which is especially feasible when the biogas is used
at or near the site of generation. Biogas methane can also be used as fuel
for vehicles, and is one of the cleanest biofuels available. For agriculture,
this lends the possibility of farm equipment being run on biogas, thus
reducing the need to purchase petroleum-based fuels like gasoline or
diesel.
Biogas can be used in ovens and lamps to heat greenhouses and at
the same time increase the carbon dioxide concentration to boost
photosynthesis in the greenhouse plants and increase yields (Kangmin,
2006).
Benefits of Using Biogas.
EnvironmentalThe conversion of biological agricultural wastes into biogas, a
domestic renewable fuel source, could help states meet renewable
energy requirements and reduce greenhouse gas emissions. Used as a
substitute for fossil fuels, such as coal and oil for electricity generation,
biogas almost immediately replaces two greenhouse gas sources;
methane released from untreated manure and coal combustion, with a
less carbon-intensive energy source in biogas combustion. While the
breakdown of methane, the primary combustible component of biogas,
through combustion does release carbon dioxide; it produces carbon
dioxide per joule delivered then either coal or oil.
Another environmental benefit is the more ecologically sound
approach to manure disposal. Manure, the waste excrement produced by
Biogas In Agriculture 3
livestock on a farm, serves as the primary raw material in biogas
production. In the United States, livestock agriculture produces over one
billion tons of manure annually. This manure is usually disposed of in
open lagoons or stored in manure piles outdoors in the open where it is
left to break down. Disposing of manure in these methods, allows for the
free release of methane and nitrous oxide, two prominent green house
gases with a combined global warming potential of anywhere from 21 to
310 times that of carbon dioxide (Cuéllar, 2008). The conversion of
manure into biogas dramatically reduces the amount of methane and
nitrous dioxide being released directly into the atmosphere, by capturing
it for use as biogas.
Further environmental benefits from the conversion of manure into
biogas and bio-slurry’ / ‘bio-sludge’ are odor reduction, the reduction of
the toxicity and pathogen potential of the manure, reduction of weed
seed germination derived from manure, conversion of manure into a safer
and more effective fertilizer, and the reduction of water contamination
from manure runoff into streams and wells (Brown, 2007).
The reduction of odors alone may ease pressures on large livestock
operations, making such operations more acceptable to permitting
agencies and local residents, which in turn may allow for even further
expansion of operations (Booz Allen Hamilton, 2007).
EnergyThe potential energy output of biogas from the livestock in the
United States could generate approximately 1% of the total energy
Biogas In Agriculture 4
consumption in the nation. On average, 33-38 kWh/day will be produced
per every 1000 ft3 of biogas (Wright, 2001).
Replacing the emissions from coal and untreated manure with that
of emissions produced from the combustion of biogas has the potential of
reducing annual greenhouse gas emissions from electricity generation in
the United States by nearly 4% (Wright, 2001). While this number could
be considered not to be a significant amount, it would be a start, and the
reduction in carbon emissions may have economic benefits to farmers.
At Royal Farms No. 1 in Tulare,
California, hog manure is slurried
and sent to a hypalon-covered
lagoon for biogas generation. The
collected biogas fuels a 70-
kilowatt (kW) engine-generator
and a 100 kW engine-generator.
The electricity generated on the
farm was able to meet monthly
electric and heat energy demands
(Abraham, 2007).
The Langerwerf Dairy in Durham, California, used cow manure was
scraped and fed into a plug flow digester. The biogas produced was used
to fire an 85 kW gas engine. The engine operated at a 35 kW capacity
level and drove a generator to produce electricity. Electricity and heat
generated was able to offset all dairy energy demands (Abraham, 2007).
Biogas In Agriculture 5
Figure 2:Langerwerf Dairy biogas facility. Source; RCM Digesters
EconomicsOne of the most prominent financial benefits from on-site bio-gas
usage on farms, is that it has the potential to make an farm energy self-
sufficient, by producing it’s own energy and not relying on outside
suppliers. There is also the potential to sell any surplus energy generated
to electric utility companies. Also available is the possible to sell bio-solids
as a fertilizer to fellow farmers. These bio-solid fertilizers are general
consider to be of better quality and more environmental safer then
petroleum based fertilizers.
A study on biogas feasibility on farms in Nova Scotia, Canada
concluded that, non-market benefits from biogas production and usage
were valued at approximately CND$15,000. These non-market benefits
are primarily composed of environmental benefits such as odor reduction
and greenhouse gas emission cuts. For smaller farms, the financial
benefit gained from non-market benefits greatly improves the financial
feasibility of on-site biogas production (Yiridoe, 2009). Other studies have
shown similar results for farms in the United States (Booz Allen Hamilton,
2007).
In the United States, farmers interested in demonstrating a cost-
effective technology for converting manure into biogas and generating
electricity may be eligible for a Renewable Energy Technology Research
and Development Grant of up to $50,000. Other incentives available
through the state's renewable energy program include technical
feasibility study grants; business and marketing grants; cash-back
rewards for installing renewable energy technologies; and an equipment
grants for non-profit organizations (Booz Allen Hamilton, 2007).
Biogas In Agriculture 6
With the introduction of carbon credit trading programs, farms using
anaerobic digesters for the conversion of biological agricultural wastes
into biogas converters receive credits for greenhouse emissions
reductions. Companies or other organizations could purchase carbon
credits from farmers using biogas in order to make up for their excessive
carbon emissions. These carbon credit-trading schemes have the
potential to supplement the income of the farmers, with the supplement
coming from a non-agricultural source. Several greenhouse gases that are
mitigated by biogas production are included in these programs, with the
carbon value of these gases converted to CO2 equivalents based on their
global warming potential (Lazarus, 2007).
Drawbacks of Biogas Usage.
EnvironmentalGreenhouse gas emissions from the agricultural industry in the
United States amounted to 536 million metric tons of carbon dioxide,
representing 7% of total carbon dioxide emissions in the United States. Of
this, 51 to 118 million metric tons of carbon dioxide are resulted from
livestock manure emissions alone, with an increase being shown in these
emissions from 1990 to 2005 (Cuéllar, 2008). The conversion of manure
to biogas will not ultimately reduce all of the 51 million tons of carbon
dioxide released from manure. When biogas is used as a fuel it breaks
down into carbon dioxide, which is then released into the atmosphere.
Biogas produced from from dairy manure typically has 0.2-0.4%
hydrogen sulfide. When placed in a low temperature environment
Biogas In Agriculture 7
hydrogen sulfide can become highly corrosive, due to it converting to
sulfuric acid (Wright, 2001).
EnergyThe electric production from biogas depends on the amount and
quality of gas as well as the efficiency of the engine appliance. Different
individual gas appliances require considerable different quality gas
standards, which makes purification and upgrading of the gas necessary.
Biogas is not easily compressed. At 2000 lbs. per sq.in it takes
about 14 gallons of compressed biogas to equal the energy value of one
gallon of diesel fuel. The use biogas for anything but continuous on site
consumption would be difficult except in large quantities.
In heating applications, methane, a component of natural gas, has a
heating value of 912 BTU/ft3, but with the methane levels in biogas being
at about 60% of the total, its heating value is 40% lower than pure
methane at about 540 BTUs/ft3 (Wright, 2001). This making biogas a less
efficient heating fuel as opposed to piped in natural gas, liquefied natural
gas, or propane.
The growing constraints on transmission lines can severely impact
renewable energy development such as biogas when a goal is the sale of
excess energy production. The nation’s transmission grid was built to
move electric power from large fossil power plants to population centers.
Challenges face the transmission of excess energy produced by smaller
scale renewable energy, like biogas. Insufficient capacity in rural areas to
move surplus electricity to distant population centers (demand centers),
Biogas In Agriculture 8
could remove any potential income from being earned (Booz Allen
Hamilton, 2007).
EconomicsBiogas production technology displays significant economies of
scale with respect to farm size. This is due to installation costs that are
fixed with respect to the size of the operation. Hence, larger farms will
gain more of a competitive edge through the use of digesters than will
small farms. As of 2007 there were no functioning digesters on U.S. farms
with less than 400 cows (Booz Allen Hamilton, 2007).
A study on the economic feasibility of on-site biogas energy
production for swine operations in Nova Scotia, Canada showed similar
results in the economies of scale. Without an incentive program, such as
low interest loans to cover start up cost or tax breaks, on-site biogas
energy production was found not to be economically feasible for many
small farms, those below 600. (Brown, 2007).
Start up cost for biogas production and usage on farms are high
with the smallest units starting at around $1,000,000. The amount of
time that a farm would take to recoup it’s investment also varies by the
size of the farm it which these units are placed, with smaller farms taking
an estimated 42 years to recoup their expenditures. For larger farms this
recouping time is estimated at less then 10 years. And while nonmarket
co-benefits could help defray these costs, it can’t be said for certain that
these some of these co-benefits will retain their value over the years need
to continue to defray the initial cost (Yiridoe, 2009) (Brown, 2007).
Biogas In Agriculture 9
And while there is the potential for carbon trading schemes to
generate income for biogas producing and using farms, it’s not a
guarantee. Carbon trading is a relatively new concept, and has yet to be
wildly adopted by either the agriculture (sellers) or industrial (buyers)
sectors, the two main players when talking about biogas. With it not being
made mandatory or some having some other policy, i.e. a carbon tax, to
induce industry to take up purchasing carbon credits, there is virtually no
income or market to trade enough of these credits to make a sufficient
regular income.
ConclusionI have no doubts that biogas is a sustainable, relatively carbon
neutral, environmentally friendly alternative fuel for the agriculture
sector. And that besides being an alternative fuel, it has substantial other
positive benefits such as helping to reduce methane emissions, making
more productive and environmentally safer fertilizers, to improving water
quality. I would have no problem also activity promoting its
implementation and usage on farms across the United States and into
Canada.
However there is one drawback and a significant one at that. As it
stands now, biogas systems are hampered by one thing, the dreaded
economy of scale. From the data that I gathered, a biogas system would
Biogas In Agriculture 10
only be effective on medium to large-scale farm operations, based upon
the number of livestock. This is a disappointment. Going from own
impressions about farming in Maryland, most farms that deal in livestock
do not have herds, and would be on the low end of a medium herd size.
Would these biogas systems be good for Maryland farmers? Well based
upon the economies of scale, I would be hard pressed to say that most
would not, just because of the cost involved. And if it was not for the cost
involved would we see more farms implement this technology? There are
programs and subsidies offered by the government to help farms of all
size to implement biogas systems. But are these funds being used
effectively? And since these funds and schemes became available, has
their been an increase in biogas systems on farms? Nothing in the data
that I have found points to one way or the other, so it’s yet to be seen.
But could we be going about this wrong. Is on-site production the
most effective way, and are we using the technology in the most effective
way? Based upon my research I would have to say no.
Biogas In Agriculture 11
In China, nearly 30,000
biogas plants supply 40 million
households with clean burning
biogas. China is looking to
supply 300 million rural
residents with electricity
generated from biogas by 2020.
Governments in Africa are
looking at biogas as a way of
reducing deforestation. In
Tanzania’s Makete District, 200
biogas plants will be
constructed. According to the
government, on average, a flock
of two cows or seven pigs or
170 poultry is sufficient to
provide enough biogas for a
family’s cooking and lighting needs (Biogas, 2009). A website I came
across, http://www.ruralcostarica.com/biogas.html, promotes small scale biogas
system construction, at what seems to be a low cost, in rural areas of
Costa Rica.
Granted we are talking about different cultures, different needs,
different cost structures, but, if these areas can put together what seems to
be comprehensive plans to increase biogas usage, what is preventing us
from doing it? Why isn’t biogas more in the renewable discussion?
Biogas In Agriculture 12
Figure 3:Small Scale Biogas system in Costa Rica. Source: Rural Costa Rica
To summarize, I do believe that has great potential, and for this
country and I think on site production and usage is the most effective way to
move forward. However until, until start-up cost go down, or significant
incentive is given to adopted the technology for small farms, the technology
is going to be predominately limited to large scale agricultural operations
Biogas In Agriculture 13
Bibliography
Abraham, E. R. (2007). Biogas : Can It Be an Important Source of Energy ? Energy , 1 (14), 67-71.
Biogas. (2009). Retrieved 11 21, 2010, from GreenTech Oppertunities: http://www.greentech-opportunities.com/Sector%20Overview/biogas
Booz Allen Hamilton. (2007). Linking Distributed Electricity Production from Alternative Energy Sources to the Traditional Generation and Transmission System. United States Department of Agriculture, Rural Development, Washington.
Brown, B. B. (2007). mpact of single versus multiple policy options on the economic feasibility of biogas energy production: Swine and dairy operations in Nova Scotia. Energy Policy , 9 (35), 4597-4610.
Cuéllar, A. D. (2008). Cow power: the energy and emissions benefits of converting manure to biogas. Environmental Research Letters , 3 (3), 034002.
Kangmin, L. &.-W. (2006, 10 6). Biogas China. Retrieved 11 21, 2010, from The Institute of Science in Society: http://www.i-sis.org.uk
Lazarus, W. F. (2007). The Economics of Anaerobic Digester Operation on a Minnesota Dairy Farm. Review of Agricultural Economics , 29 (2), 349-364.
Weiske, A. V. (2006). Mitigation of greenhouse gas emissions in European conventional and organic dairy farming. Agriculture, Ecosystems & Environment , 112 (2-3), 221-232.
Wright, P. (2001). Overview of Anaerobic Digestion Systems for Dairy Farms. Natural Resource, Agriculture and Engineering Service (15).
Biogas In Agriculture 14