Biogas In AgricultureThe Potential for Livestock Waste to Act as an Alternative Source of Energy

Jason Boothe

GEOG 317, Fall 2010Dr. TashDecember 9, 2010

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Biogas In Agriculture ii

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

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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

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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.

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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

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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

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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).

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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).

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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

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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.

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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?

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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

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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.

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