Turning your old banana peels and last night's leftovers into biogas sounds like a win-win situation for you and the environment: You don't have to feel guilty about having cooked too much pasta, and the use of biogas reduces CO2 emissions when it replaces fossil fuels.  But a new study from the Norwegian University of Science and Technology (NTNU) shows that it's not that simple. 

In fact, encouraging people to work harder to cut food waste instead of collecting food waste and turning it into biogas cuts energy impacts more than biogas production and use, the researchers found.  Of equal importance, cutting food waste also helps cut the use of phosphorus, which is an increasingly scare but essential plant nutrient that is a key component of fertilizer. This matters because fully one-third of all food produced globally ends up as waste.  "Our work shows that policy and incentives should prioritize food waste prevention and that most savings can be had through a combination of prevention and recycling," said Helen Hamilton, a PhD candidate at the university's Industrial Ecology Programme.

Hamilton and her colleagues at the Industrial Ecology Programme used Norway as a case study to evaluate the costs and benefits of recycling food waste versus preventing it. The group looked at what they called "avoidable food waste," or food that should have been eaten but for different reasons ends up as waste. The term does not include unavoidable food waste, such as bones, shells, peels and residues, like coffee grounds (...) "It is important that we address these issues now because there's a risk," she said. "If we prioritize food waste recycling and build up facilities for producing biogas, we risk locking ourselves into needing waste. That is clearly not part of a sustainable future."  More information: Helen A. Hamilton et al. Assessment of Food Waste Prevention and Recycling Strategies Using a Multilayer Systems Approach, Environmental Science & Technology (2015). DOI: 10.1021/acs.est.5b03781

http://phys.org/news/2016-01-food-strategy-biogas.html

Waste Framework Directive 2008/98  Article 4 Waste hierarchy

1. The following waste hierarchy shall apply as a priority order in waste prevention and management legislation and policy: (a) prevention; (b) preparing for re-use; (c) recycling; (d) other recovery, e.g. energy recovery; and (e) disposal.

2. When applying the waste hierarchy referred to in paragraph 1, Member States shall take measures to encourage the options that deliver the best overall environmental outcome. This may require specific waste streams departing from the hierarchy where this is justified by life-cycle thinking on the overall impacts of the generation and management of such waste.

http://ec.europa.eu/environment/waste/framework/