Methane as a Greenhouse Gas (GHG)
Methane is responsible for about 18% of the enhanced greenhouse effect'.
According to the Intergovernmental Panel on Climate Change, methane concentrations
now are at their highest levels in 420 000 years2. Although there is
considerably less methane than carbon dioxide in the atmosphere, it is
a serious problem. Methane is 21 times more effective at trapping heat
than carbon dioxide.
GHG's and the Hog Industry
Manure in storage and on land is a significant source of methane emissions.
When manure decomposes in the absence of oxygen (anaerobic), much of
it is converted to methane gas. When oxygen is present (aerobic), decomposing
manure releases nitrous oxide, another potent GHG.
Manitoba's livestock industry in growing. The sale of Manitoban hogs
increased from 4.3 million to 5.3 million head from 1999 to 2000. A full-grown
pig produces 4.5 kg or 10 Ibs of manure a day. Projects to reduce emissions
from hog manure offer a considerable opportunity to start meeting GHG
reduction commitments under the Kyoto Protocol.
At the "Greenhouse Gases and the Hog Industry" workshop (December
9, 2002), the Canadian Pork Council (CPC), along with participants from pork
and farm associations; federal and provincial departments of agriculture, environment
and natural resources; agrologist institutes; research centres and Chairs of
pork-related congresses identified priorities in the development and application
of GHG reduction technologies for the pork sector. They include 3:
· Projects should consider whole farm applications
· Projects should be applicable to small and large scale farming operations
· There is a need to focus on handling, storing, and covering manure
· Demonstrations for N use efficiency anaerobic digesters were recommended.
Biogas recovery systems have been identified as one of the most promising areas
of development for the significant reduction greenhouses gas emissions from
agriculture. Biogas recovery systems are also known as anaerobic digesters.
During anaerobic digestion, microorganisms break down manure in an oxygen-free
environment. One of the natural products of this process is biogas. Biogas
typically consists of 60 to 70 percent methane, 30 to 40 percent carbon dioxide
1 Kinsmen, R.G., F.D. Sauer, H.A. Jackson, H.K. Patni, D.I. Masse, M. Wolynetz
and J.A. Munroe. 1997. Methane and carbon dioxide emissions from lactating
Holsteins. Dairy and Research Report, Centre for Food and Animal Research,
Z Jouzel, J. and D. Raynaud. 1999. COa and Temperature over the Last 420,000
Years: Present and Projected Climate Changes in Perspective. USGCRP Seminar.
3 Canadian Pork Council. 2002. Green House Gases and the Hog Industry. Workshop
Proceedings, Dec.9 2002.
amounts of other gases4. Depending on digester design, methane content
can reach as a high as 95%.
Benefits of Biocias Recovery
Captured biogas can be used to generate heat, hot water or electricity. As
such, recovery systems significantly reduce energy costs for both private and
commercial operations. As such, the use of biogas recovery systems fits with
AAFC's Sustainable Development Strategy: "by 2006, there will be an increase
in the ratio of agricultural output energy over input energy"5.
Biogas can also be flared to control odour if energy recovery is not feasible.
Both flaring and energy production reduce greenhouse gas emissions.
Other benefits to biogas recovery include:
· Odour control - the effluent odour from anaerobic digesters is significantly
less than odours from conventional manure management systems. Odour reductions
of 98 percent have been achieved by pilot digester projectsb.
· Water quality protection - when digesters are properly managed, phosphorous
and metals settle out. When processed manure is applied to the land, these elements
are left behind, keeping them out of surface waters. Digesters are also made
of concrete or steel, protecting water from pollution with pre-treated manure.
· Public health protection - heated digesters isolate and destroy disease-causing
organisms that might otherwise contaminate surface waters and pose a public health
· High quality endproducts - anaerobic digesters reduce ammonia losses.
Digested manure can contain more valuable nitrogen for crop production.
Biogas recovery systems have four basic components: a digester, a gas-handling
system, a gas-use device and a manure storage tank or pond to hold the treated
effluent prior to land application. Digesters can effectively process manure
in 2-3 days or 25-30 days', depending on the technology used. There are three
types of digesters:
· A complete mix digester is a heated tank of either reinforced steel
or concrete, with a gas-tight cover. The contents are mixed periodically by a
motor-driven impeller or a pump. This type works best with slurry manure (typical
of hog operations) with total solids content between 3 and 10 percent.
· A covered lagoon digester is an earthen lagoon fitted with a cover that
collects biogas as it is produced. They are best suited for manure collection
4 EPA. 2002. Managing Manure with Biogas Recovery Systems: Improved Performance
at Competitive Costs. The AgSTAR Program. Office of Air and Radiation (6202J).
5 AAFC. 2001. Agriculture in Harmony with Nature: AAFC Sustainable Development
Strategy II, 2001-2004. Publication 2074/E. http://www.agr.ca/policy/environment.
6 Zhang, Q. 2002. Odour Test Report. In Field Test Demonstration of SEI Hog
Manure Treatment Technology: Final Report. G. Lakshman. Pp 14-16.
7 ONR Environmental Systems. 2002. ONR Agri-Design: Anaerobic Digester Technology.
ONR Product Information Sheet Rev.OlAND, http://www.onrsystems.com
very low solids content. Because they are not heated, they do not produce
adequate biogas flow for energy production during colder months.
· A plug-flow digester is a long, narrow heated tank - often built below
ground level - with a gas-tight cover. They are used only for dairy manure, and
require thick manure ranging from 11 to 13 percent solids. As this design is
not relevant to hog operations, it will not be discussed in subsequent sections.
Biogas Recovery System Costs
Cost depends on the size of the operation. The larger the operation, the lower
the per unit cost of the biogas recovery system. The Environmental Protection
Agency suggests a break-even herd size of 2500 hogs for a complete mix digester,
and 1350 hogs for a covered lagoon digestera.
On a per unit basis, heated digesters cost approximately $200-420 CDN per hog
and covered lagoon digesters cost $200 - 400 CDN per hog'. Biogas recovery
systems have a payback period of 3 to 7 years when biogas products are used
for energy production.
Canadian Technology Providers
There are currently three Canadian companies that design/build biogas recovery
systems, provide technology, and offer consulting services:
ONR Environmental Systems Inc.
Site 17, Box 2, RR 1
Okatoks, AB T1S lAl
Ph: 403-540-6541 Fx: 403-938-2715 e-mail: email@example.com
Clear-Green Biotechnologies Inc.
13-1724 Quebec Avenue Saskatoon, SK
Ph: 306-931-2610 Fx: 306-931-6610 e-mail: firstname.lastname@example.org
RENTEC Renewable Technologies, Inc.
342 English Settlement Road
Trenton, On K8V 5P7
Ph : 613-849-9199 Fx: 613-475-0361 e-mail: email@example.com
e EPA. 1997. AgSTAR FarmWare Software, Version 2.0. FarmWare User's
9 EPA. 1999. Final Report on U.S. Methane Emissions 1990-2020: Inventories,
Projections and Opportunities for Reductions. Section 5. EPA-430-R-99-013.
For additional Canadian and international technology providers, digester
information and an inventory of manure digester programs and projects,
visit: http://res2.agr.ca/initiatives/manurenet/en/man digesters.html.
Canadian Pork Council
1101-75 Albert Street Ottawa, ON
Ph : 613-236-9239
Approximately $623 000 per year will be available for the hog industry
from 2003 to 2006 (3 years). The CPC has issued calls for proposals for
activities that will assist in the adoption of new practices or technologies
by farmers to address greenhouse gas emissions.
The Canadian Adaptation and Rural Development Fund (CARD)
Dr. Les Haley, Chair
Climate Change Funding Initiative in Agriculture Canadian Agri-Food Research
Building 60, Central Experimental Farm
Agriculture and Agrifood Canada
930 Carling Avenue, Room 481
The Climate Change Funding Initiative (CCFI) is a four-year, $4 million
investment to help the agricultural sector address climate change and
ultimately help contribute to Canada's efforts to meet its Kyoto commitments
to reduce GHG emissions to six percent below 1990 levels by 2008-2012.
research and development areas include manure management, carbon sequestrations
Biogas Recovery - A Scalable Technology
Biogas recovery technologies have applications beyond the barn. In Kristianstad,
Sweden, biogas plants are used to co-digest municipal solid waste with manure
and other organic biomass for the production of energy and fertilizer. The
project offers a feasible and sustainable solution to waste problems in many
10 CADDET Centre for Renewable Energy. 2000. Co-Digestion of Manure with Industrial
and Household Waste. Technical Brochure No. 118. http://www.caddet-re.org.
· Built on the site of a closed-down sugar beet factory, tanks from the
former sugar wastewater treatment plant are re-used as digestion and storage
tanks. Kristianstaders separate their organic waste into paper bags, which are
collected by municipal services. In 1998, 3100 tonnes of household waste was
collected and digested from 100 000 households.
· Industrial waste is also processed at a cost of approximately $65/tonne
(CDN). A total of 41 200 tonnes of manure (hog, cattle and poultry), 24 600 tonnes
of abattoir waste and 900 tonnes of distillery waste was processed by the municipal
digester in 1998.
· Gross biogas recovery for 1998 was 20 000 MWh. 2 100 MWh were used to
heat the digester. 17 900 MWh were sold to the district heating plant.
This type of technology may be appropriate for small municipalities
whose landfills are not large enough support a methane recovery operation.
It also reduces the amount of waste that enters landfills.