Managing Animal Waste to Recover Methane
 

International Opportunities for Project Development
 

Methane is both the primary constituent of natural gas and 

a potent greenhouse gas when released to the atmosphere. Reducing methane emissions can yield substantial economic, environmental and energy benefits. In the agriculture 

sector, the implementation of anaerobic digestion technology 

can lead to improved air and water quality, odor control, 

improved nutrient management, a reduction in greenhouse gas 

emissions, and the capture and use of biogas—a source of 

clean, renewable energy. The Methane to Markets Partnership 

is building public and private sector alliances to advance the 

recovery and use of methane at livestock manure management 

operations around the world. 

BACKGROUND ON GLOBAL EMISSIONS 

Methane is produced and emitted during the anaerobic 

decomposition of organic material in livestock manure. 

Globally, livestock manure management contributes more than 

230 million metric tons of carbon dioxide equivalent 

(MMTCO2E) of methane emissions, roughly 4 percent of total 

anthropogenic (human-induced) methane emissions. Three 

groups of animals account for more than 80 percent of total 

emissions: swine (40 percent); non-dairy cattle (20 percent); 

and dairy cattle (20 percent). In certain countries, poultry is 

also a significant source of methane emissions. Figure 1 represents Partners and other countries with significant methane 

emissions from livestock manure management. 

While current estimates indicate that developed countries 

account for the largest percentage of total methane emissions, 

emissions from developing countries are substantial, and their 

share of emissions is expected to rise along with industrialization and population growth. The key factors driving methane 

emission increases in the developing world are the growth in 

livestock populations necessary to meet the expected worldwide demand for dairy and meat products and the trend 

toward larger, more concentrated commercialized livestock 

management operations. These larger and more intensive 

operations typically utilize more liquid-based manure management systems, which produce higher methane emissions. 

RECOVERY AND USE OPPORTUNITIES 

Methane released from liquid manure management systems 

can be captured and used as a clean energy source to produce electricity, heat, or combined heat and power; in fuel 

gas-fired equipment such as engines, boilers, or chillers to 

meet a portion of the farm’s energy requirements; or simply 

flared. Project development in this sector can help to reduce 

greenhouse gas emissions and provide alternative energy 

sources while also providing opportunities for agricultural 

diversification and wider environmental benefits. 

Techniques for recovery 

include covered anaerobic 

lagoons, plug flow digesters, 

complete mix digesters, and 

small scale digesters. The 

waste handled is in the form 

of liquid, slurry, or semi-solid, 

depending on the system 

design requirements. The 

following are brief descriptions of conventional anaerobic 

digestion technologies: 

• Covered anaerobic lagoons are constant volume reactors 

that can be operated at ambient temperatures. Manure is 

treated under anaerobic conditions producing methane, 

which is recovered by using impermeable floating lagoon 

covers and applying negative pressure. 

• Complete mix digesters are heated digesters constructed 

of concrete or steel designed to enhance anaerobic 

decomposition and maximize methane recovery. 

United States (17%) 

India (10%) 

China (9%) 

Germany (8%) France (6%) 

Spain (4%) 

Brazil (4%) 

Turkey (3%) 

Russia (3%) 

Italy (2%) 

All Others (22%) Mexico (1%) 

Philippines (1%) 

Nigeria (1%) 

Australia (1%) 

Argentina (1%) 

Ukraine (1%) 

United Kingdom (1%) 

Thailand (1%)

Canada (2%) 

Vietnam (2%) 

Pakistan (2%) 

Covered Anaerobic Lagoon 

Source: Global Anthropogenic Emissions of Non-CO2 Greenhouse Gases 1990-2020 

Figure 1: Estimated Global Methane Emissions from Livestock 

Manure Management, 2005. 

Total = 234.57 MMTCO2E 

www.methanetomarkets.org 1 March 2008 

(EPA Report 430-R-06-003) 

Recycled/Recyclable—Printed with vegetable oil based inks on 100% postconsumer, process chlorine free recycled paper. 
• Plug flow digesters are heated systems that operate at 

a constant temperature year round, producing stable gas 

• Improving and facilitating access to capital to support 

project investment. 

flows that support gas-to-energy applications in all climates. 

•	 Small-scale digesters are small-scale versions of the 

above three types and are well suited for smaller farms in 

regions with technical, capital, and material resource 

constraints. 

•	 Cooperating with Partners to improve markets and provide 

legal and regulatory frameworks that encourage project 

development. 

Anaerobic digestion can be cost-competitive when compared to 

conventional waste management practices. These systems can 

have payback periods of three to seven years when energy gas 

uses are employed as opposed to conventional waste systems, 

which do not pay back and represent sunk costs to the farm 

enterprise. In short, current technology offers a wide range of 

opportunities to abate livestock manure methane emissions at no 

cost or even while generating an alternative income source. 

Digesters also provide water quality benefits, by significantly 

decreasing or eliminating the run-off of animal wastes into water 

bodies and groundwater recharge areas, which is a growing concern in many parts of the world. 

ISSUES FOR PROJECT DEVELOPMENT 

Although there are several effective ways to reduce methane 

emissions in the agricultural sector, there are also several important issues to consider for successful project development. Some 

of these include: 

• Recognizing anaerobic digestion systems as a core 

business opportunity and directing available capital 

towards methane reduction projects. 

• Providing valid information on and access to the many 

available commercial management practices. 

• Ensuring that technologies appropriate to the local climate 

and waste handling method are used. In general, ambient 

temperature systems such as lagoons and fixed domes for 

farms are the preferred technologies for latitudes between 

30 degrees north and 30 degrees south. Alternatively, heated systems such as plug flow digesters are better suited 

for latitudes above 30 degrees north and below 30 degrees 

south. 

Addressing these important issues and facilitating project 

development in the agricultural industry is a primary focus of 

the Methane to Markets Partnership. The Partnership will work 

to overcome barriers to project development by: 

• Engaging the livestock industry to improve awareness 

of methane reduction opportunities through anaerobic 

digestion techniques. 

• Facilitating and enhancing the application and broad 

adoption of methane reduction technologies and management practices. 

Case Study: 

The Global Environment Facility in China 

In China, methane emissions from livestock manure contribute 10.4 percent of the country’s total human-induced 

greenhouse gas emissions. Beginning in 2006, the Global 

Environment Facility, through the World Bank, will provide 

a $7 million grant over five years to support a comprehensive approach to reduce the significant environmental and 

health damage from increasingly concentrated livestock 

production. The proposed project (involving China, 

Thailand, and Vietnam) will integrate policy development 

and implementation, technological solutions and capacity 

building, and regional connections.The project will receive 

technical support from the United States Environmental 

Protection Agency. Its global environmental objective is 

to reduce livestock-induced, land-based pollution and 

environmental degradation of the South China Sea. 

The grant will provide on-the-ground demonstrations of 

innovative, cost-effective livestock waste management 

technologies by private livestock producers. A successful 

project in China will be replicated within the country and in 

other countries with similar industrial practices and contribute to the protection and sustainability of one of the 

world’s most biologically diverse regions. 

Small-Intermediate Scale Digester 

www.methanetomarkets.org 2 March 2008 

Printing was provided by the U.S. Environmental Protection Agency in its capacity as the Administrative Support Group for the Methane to Markets Partnership.