Germany wants to curb the use of unsustainable crops for biomass and force producers to better utilize animal dung and organic waste, a move which has prompted warnings from the industry. While only about a third of animal manure is currently utilized for biogas production, the government wants two thirds to be used by 2030, a draft strategy paper says. It also wants organic waste and cover crops to play a greater role in bioenergy, while plant operators typically prefer to use energy crops such as corn or wood to produce heat, power or biofuels. Biomass, which is the main renewable energy source in both Germany and the European Union, has been considered a controversial alternative to conventional fossil fuels. While proponents argue that burning trees and plants — which absorb carbon dioxide — results in lower net emissions, critics worry about deforestation, land use and biological diversity.