Some weeks ago I took a picture of my kitchen waste. It’s not exactly nice to look at – but it contains a great potential for making the world a better place!
If we use it the right way, it could provide the world with sustainable fuels and at the same time increase food production for a growing global population. Anaerobic digestion is a process that could make this happen.
Replacing fossil fuels
When you look at it, it’s just som potato peels, some carrot peels, the top of a pineapple, an egg shell, some apples that were no good any more, a few pieces of bread, some cabbage leaves and other vegetables and fruit waste.
But a part of it could be turned into biogas which could become fuel for your car, or it could be used to generate electricity for your computer and heat for your home – and thus replace fossil fuels that are becoming an increasingly great burden to the global society.
When the biogas has been extracted from the organic waste, the remains could be used as a fertilizer. This means that the nutrients would be recycled to the soil that they came from when the carrots and potatoes were harvested. This organic fertilizer could replace chemical fertilizer being an important step forward for our world’s ability to provide the necessary food for a growing population.
According to the report “Resilient People, Resilient Earth,” The United Nations expect that demand for food will rise by 70 percent by 2050. The reason is a global population expected to grow from 7 billion this year to more than 9 billion by 2050.
Among a lot other things, this means that we will need a lot more phosphorus to make a lot more crops grow in order to make food for all these people.
Phosphorus – a limited resource
Plants can’t grow without phosphorus, and there is only so much of it in the world. Today phosphorus is primarily taken out of mines in places like Morocco, Russia, the USA and China. It has been estimated by research scientists that the current quality and quantity of available phosphorus will last another 40 years. After this period of time, we will see quality going down and prices going up.
At the moment we are not keeping phosphorus for the future. We let it run through our rivers into the oceans where it’ll be really difficult to retrieve. In Denmark we incinerate our waste, and a part of the ashes is put into concrete which is used to construct buildings. In order to get this phosphorus back when it has become a scarce resource once in the future, we’ll have to tear the buildings apart. Is this common sense?
This problem could be solved if we put our food waste and agricultural waste through an anaerobic digestion process and used the remains – the digestate – as fertilizer.
Another important nutrient is nitrogen. The production of nitrogen for chemical fertilizer takes a lot of fossil fuel and recycling the nitrogenous contents in food waste as fertilizer would reduce the consumption of fossil fuels.
Are we moving fast enough?
I have been writing an article for the Danish bioenergy magazine (Bioenergi Magasinet) about anaerobic digestion of municipal solid waste in Europe.
In this article I quote Bruno Mattheuws from the Belgian business Organic Waste Systems (OWS) who is regularly measuring how municipal solid waste is being treated in Europe.
According to OWS the capacity for anaerobic digestion of municipal solid waste has been growing steadily since 1990 and has now reached 6 million tonnes per year. This is positive but still only a fraction of the potential. The question is: are we moving ahead quickly enough?
Let me know what you think!
Poul Erik Pedersen