Turning 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 carbon dioxide emissions when it replaces fossil fuels.
But a new study from the Norwegian University of Science and Technology shows that it is not that simple. In fact, encouraging people to work harder to cut food waste, instead of collecting food waste and turning it into biogas, have more impact on energy, the researchers found.
Of equal importance, cutting food waste also helps cut the use of phosphorus, an increasingly scarce but essential plant nutrient that is a key component of fertiliser. This matters because one-third of all food produced globally ends up as waste.
“Our work shows that policy and incentives should prioritise 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 used Norway as a case study to evaluate the costs and benefits of recycling food waste into biogas 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 excludes unavoidable food waste, such as bones, shells, peels and residues, like coffee grounds.
Looking at different segments of the food production and consumption sector, they found that 17% of all sold food was wasted. Most of that waste was at the consumer level, partly because of the confusion caused by labelling, the researchers wrote in an article in Environmental Science and Technology.
“Consumers often mistake ‘use by dates’, which refer to highly perishable goods that pose a risk to human health if consumed after a certain period, with ‘best before dates’ which merely indicate a food’s reduction in quality but not safety,” Hamilton and her colleagues wrote. “This results in a substantial amount of food waste at the household level.”
They also looked at how food waste affected phosphorus use in the agriculture sector. Phosphorus, which mainly comes from phosphate rock, is a limited resource that is primarily concentrated in geopolitically unstable regions including Morocco and the Western Sahara. It is an element, so it can’t be created. It is also necessary for food production, and has no substitute.
When Hamilton and her colleagues compared what happens to phosphorus demands if food waste is prevented instead of recycled, they found that Norway’s need to import mineral phosphorus declined by 14%.
The need for imports also decreased compared to the baseline demands by 6% under the food waste recycling scenario, but that is a theoretical maximum, and would only be true if the leftovers from biogas processing could be perfectly returned to agricultural soils as fertiliser, which is not the practice today.
Better to not waste food
Some of Norway’s major cities collect food waste in separate green bags. The city of Tromsoe composts its waste, while Oslo has its own biogas facility that relies in part on food waste collected in the city.
Some of the biogas that is generated by the Oslo facility is used to run 36 buses, which led the bus company, Ruter, to proclaim in October 2013 that “now buses are fuelled by your banana peels.”
While that sounds like a good thing – it does, in fact, reduce the need for fossil fuels – in sum, it takes more energy to collect the food waste and process it than it would if people didn’t throw away so much potentially edible food unnecessarily, Hamilton and her colleagues found.
Given the obvious costs of collecting food waste and building biogas plants, why isn’t there a more concerted effort to reduce food waste in Norway?
Hamilton points to two reasons.
The first is that while there are some efforts in Norway to cut food waste, there are no clear goals or targets at the national level. That reduces the imperative to promote cutting food waste.
The second reason is far more subtle, and built into the very fabric of our society, she says.
“Our current society is shaped to favour the throughput of material, with the production of marketable goods, like food and biogas, providing profitability for businesses,” she and her co-authors wrote.
“Because of this, there is a ‘clear temptation’ to prioritise the use of food waste for energy recycling over food waste prevention.”
Targets and funding
The fallout from these two factors is clear in Norwegian government spending, she says. Last year, lawmakers allocated 10mil Norwegian krone (RM4.9mil) to biogas pilot projects and research. Two biogas facilities have opened over the past three years that are specifically for organic/food waste. Government support for the two facilities has topped 9.3mil krone (RM4.6mil), while the country’s largest food waste prevention effort, called ForMat, was allocated just 700,000 krone (RM348,630).
Hamilton and her co-authors blame this mismatch on policy-makers’ narrow focus on solving the problem.
“If one only analyses the methods for handling wastes without regards to upstream impacts, the results will often reflect the benefit of producing secondary value added goods, such as biofuels,” they wrote.
Prioritising recycling also raises the risk of being locked into “needing” waste to run the biogas facilities, Hamilton said.
“That is clearly not part of a sustainable future.” – Norwegian University of Science and Technology