Food is the basis of all forms of economy – financial and ecological. Protection of our agricultural land, and with it protection of our soil, is the key to the survival of all species. Everything we are, everything we ever will be is predicated on what we eat, and most of what we eat comes from the soil.

But society is losing its connection with the soil and with the farming community as our food producers. We no longer recognise that everything we eat has to be grown and, at the same time, almost everything we eat produces organic waste. It may seem counter intuitive, but the greatest single tool we have to reconnect to our soils is this waste itself.

Waste in the food cycle occurs at the stages of production, processing, preparation, consumption and digestion. The 2011 Global Food Loss and Waste study pointed out that more than a billion tonnes of edible food was being wasted each year, while nearly one billion people globally were affected by hunger. These figures suggest that there should be enough food in the world to feed the hungry, so how can we reduce waste and at the same time improve our food supply chain?

Starting at the beginning of the food cycle – the point of production – it is clear that some plant parts cannot be used as food but can be fed straight back into the system. Plant stubble and stems left in the field, skin peelings and offcuts from food processing are mostly discarded before the vegetable or fruit becomes a saleable commodity. This organic matter is a valuable part of the food chain if returned to the soil as compost. It can go directly back into farm soils as a valuable biological product.

Once a food product leaves the farm and before it reaches the plate there are many opportunities to reduce waste. Offal and other unused meat can become animal feed, while unsold food can go to charity to feed the poor: out-of-date food is often still edible. But even after these uses, vast quantities of organic waste remain. Much of it currently goes into landfill, where it generates massive quantities of greenhouse gas. But this unwanted matter is also potential food for the soil.

The ability of soil to sustain food production relies on its biological activity, which delivers nutrients to plant roots. However even if artificial fertiliser is in use, a more biologically active soil will ensure the fertiliser is used more effectively and efficiently. Organic compost, produced from food waste, is an ideal means of improving this biological activity, and thereby the soil’s fertility.

Collecting organic waste

Those of us who are already home or community gardeners have long ago seen that the best use for any organic waste is as quality compost, returned to our gardens as food for the soil. But for people in the cities without gardens how do we get their vast amounts of organic waste back into the farmers’ soils to help produce more food for the broader community?

A process developed in Australia has done just that. City to Soil, a project of Groundswell which seeks ways to return organic waste to soil, takes clean source-separated, compostable food and garden waste and turns it into a high quality compost using a simple system that requires very little manual labour and minimal machinery.

Food waste, including all meat and dairy, is collected from kitchens in a small caddy lined with a fully compostable bag. The bag containing the food is placed into a collection bin with yard waste. The focus of the system is to keep the compost free from contaminants such as metal, plastic and glass. The message to householders is ‘we need this organic waste clean because it is going into soils to grow food’. And householders clearly get the message because the contamination level has never risen above 0.4%.

Processing organic waste into compost

The City to Soil compost process is based on the work of Sir Albert Howard’s Indore compost method. The organic matter is wetted down, inoculated with beneficial microbes and covered with a tarpaulin or waterproof sheet. It then goes through the first aerobic stage, using just air to break it down. The heap will build up a temperature of 60°C or over, and can stay hot for weeks at a time.

After this initial phase the compost begins to ferment, and the process at work on the organic matter switches from aerobic to anaerobic. This second stage produces vast quantities of microbial life forms, which live and die in rapid cycles, thereby building up the compost’s humus levels.

The heap has a small dip in the top of the cover so that the moisture caused through respiration (as the compost breathes) collects and drops back into the heap to minimise the amount of added water required in the process.

This composting method in many instances requires no shredding and little if any turning. The entire process can be achieved with or without machinery, depending on the scale. A farmer using this process needs little more than a tractor and a cover.

The intense and diverse biological activity in the compost process means all the gases produced by one form of biology are consumed by another. As a result no odour and very little methane is produced, in stark contrast to the gases released when organic matter is added to landfill.

Using the same investment and infrastructure we currently use for rubbish collection and disposal, we can separate out our organic waste to create a high quality, biologically active compost. In the process, we can divert the money paid to landfill sites into creating new jobs that protect our soils. We rely on a very thin skin of soil on the surface of the earth to produce our food and sustain life. It is an invaluable resource, and it warrants our protection.

Photograph: Steph French

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