Unlike Europe, experience with AD in North America is still limited. AD in North America only began in late 1970s to control the odor in farms (Lusk, 1998). Recently, the anaerobic digesters for manure stabilization and energy production has improved a great deal. The number of operating farm-biogas plants increased from 25 in 2000 to 176 in 2011. Biogas from farm digesters provided sufficient heat to the farms and generated 541 million kWh of electricity in 2011 (Costa and Voell, 2012). In addition, 594 US municipal solid waste disposal facilities and 1238 municipal wastewater treatment plants are collecting biogas from the sites, recovering 155 billion MJ of energy for heat and electricity. This in turn reduced 99 million metric tons of greenhouse gas emissions, which is about 4% of the greenhouse gases produced by US (Kumar et al., 2015). In Canada, the Ontario government implemented a Renewable Energy Standard Offer Program in 2006, which provides farmers a higher rate for biogas-produced electricity. According to this program, farmers are financially assisted to reduce the costs of digester construction (Hilborn et al., 2007). On the other hand, AD is less promoted in Manitoba due to the well-established and cost-effective hydroelectricity industry in that region (Wohlgemut, 2006).

In Latin America, many biogas plants operate in the agricultural, industrial and municipal sectors. Biogas is mainly used for cooking, lighting, and as fuel for vehicles. Brazil had 25 biogas plants connected to the electricity grid in 2014 and the production of electricity from biomass corresponded to 8.75% of the Brazilian electricity production (IEA-Members, 2015). In Mexico, farm-based digesters are widespread, generating energy from cow manure (Kumar et al., 2015).

In Africa, there are attempts by international organizations and foreign aid agencies to promote biogas technology. Some digesters have been installed in some sub Saharan countries to convert feedstocks, such as slaughterhouse waste, municipal waste, industrial waste, and manure to biogas. Small-scale biogas plants have been established all over the continent but only a few of them are in use (Parawira, 2009). Insufficient know-how concerning anaerobic technology is claimed to be the main reason for inadequate operational potential of the installed plants. In some cases, the installation of the plant is of poor quality and lacking appropriate maintenance.

In Asia (mostly China and India, but also Vietnam, Thailand, etc.) there are millions of low-tech, hand-made plants consisting of underground, noninsulated digesters in operation for decades. Manure and food residues are the main feedstocks used and the biogas energy generated is used for cooking and lighting. In order to support the development of renewable energy sources, China enforces suitable legislation and takes steps to promote the industrialization of the construction of biogas plants. In 2009, about 34,000 small-scale biogas plants and 22,900 medium- (MLBGPs, fermenter >50 m³) and 3717 large-scale biogas plants (fermenter > 300 m³) were installed. The biogas project of China is forecast to increase to 10,000 livestock farms and 6000 industrial plants by 2020 (Kumar et al., 2015). In Korea, there are 82 biogas plants, producing electricity (2578 GWh per year) particularly from landfills and sewage sludge. There are 15 new biogas plants under construction to treat 4764 tons of food waste and food waste leachate daily to produce 454 GWh biogas by 2017 (IEA-Members, 2015). In India, there were over three million family-sized biogas plants in 1999. The Indian Government provided financial assistance in order to build nearly four million family-sized biogas plants by the end of 2007 (Bond and Templeton, 2011). Nowadays, there is a trend toward using bigger and more sophisticated digesters with improved biogas productivity and digester cleansing convenience (Kumar et al., 2015). The ministry of nonconventional energy resources implements a program (national biogas and manure management program) for providing financial, training and technical support for the construction and maintenance of biogas plants. Similar initiatives have been taken in Nepal and Vietnam (Van Nes, 2006).

In Australia, electricity generation from biogas has been increased from 1605 GWh to 3234 GWh from 2000 to 2007 (UN-Statistics-Division, 2010). Wastes from food processing plants, livestock manure, and human sewage are the primary feedstocks for biogas production. Most of the installed capacity is at sewage treatment plants, which are considered highly cost-effective.

The future of biogas as a competitive biofuel relies on the economic feasibility of the anaerobic technology. The income sources of a biogas plant are the energy and fertilizer sales as well as the tipping fees for receiving off-farm waste. Remuneration or subsidies from the government is an extra income. If the cost of energy production is too high, biogas can be burned to eliminate odors and greenhouse gas emissions, but this is not a viable option. The biogas production cost is distinguished into the capital (or investment) and operational expenses for the installation of the plant and its maintenance, respectively. Capital costs are determined mainly by the plant size and the technology selected. The prices of components (feeders, stirrers, CHP, etc.), construction materials (concrete, steel) and also process monitoring equipment affect the investment cost. The operational costs include maintenance of the biogas plant, labor costs, insurance, and other utilities. Laaber et al. (2007) estimated that the capital costs vary between 3000 and 5000 €/kW electricity for the AD of energy crops.