waste

Safi Sana’s circular economy waste business

One of the core principles of a circular economy is that waste is a resource. Rather than being thrown away, we should look at ways to use it as an input for another process. Safi Sana are applying this line of thinking in Ghana.

Their factory takes in 25,000 kg of organic waste every day from the city of Accra. That includes waste and scraps from food markets and slaugherhouses, and waste from public toilets in slum districts. It all goes in a large digester, which harvests biogas. The gas is burned to produce electricity, which is sold straight into the grid – Safi Sana is the first biogas plant in Ghana with a grid connection.

As well as clean energy, the residues from the digester are turned into compost, which is sold on as an organic fertilizer or used on site in a plant nursery. Wastewater is purified and used for irrigation.

Waste processing of this kind is often left to local authorities, or relies on development aid to build the infrastructure for it. In this case, Safi Sana sells electricity, fertiliser, seedlings and clean water, and runs as a profitable business.

According to UN Environment, the amount of municipal waste generated in Africa is expected to double between 2018 and 2025. That’s a huge waste processing challenge, with serious consequences for health, quality of life, and the quality of the natural environment and wildlife. It will be much easier to solve if waste is taken as an opportunity to create businesses, jobs, and economic development.

This isn’t just a problem for Africa though. In the west we still flush toilets with drinking water, and usually treat sewage as a problem to be solved rather than a business opportunity. Outside of festivals and campsites, there is almost zero interest in innovation around toilets. It’s not something we want to think about.

Organic waste is the same. Where I live in Luton, 40% of the average household’s ‘black bin’ rubbish is food waste. Despite having plenty of potential for biogas, energy and compost, that is currently mixed in with everything else and goes either to landfill or incineration. The council say that separate food waste collection isn’t economical, but you have to wonder why that’s the only option. It seems like there are lots of missed opportunities in Britain’s waste system at the moment, and I’d be interested to see what a version of Safi Sana would look like in a UK context. (I expect somebody’s doing it already and I haven’t heard about it yet, so tell us about it if you know a good project.)

 

3 comments

  1. I try to maintain a ‘circular’ scheme in our very small terraced house garden – the whole plot, including the house, is just 6×30 metres. Additional input is uncooked food waste (we are vegetarian) and swept up leaves from trees in the adjacent park. Virtually the only output is clippings from our bay tree, which is almost impossible to compost. From this modest space, every year I make a couple of hundred litres of potting compost for all the patio pots. All the waste compost in turn builds up raised beds down each side of the mainly paved garden which maintain very healthy shrubs and fruit trees – the prunings from which go back round.
    Also I do some gardening work for a local business in what are essentially car parks with planted verges. This is three Victorian houses in a leafy suburb of Sheffield each with 40 metre gardens. From this, every year I get a cubic metre of leaf mould from all the street trees and half a cubic metre of compost which goes to a local allotment where they rave about the quality of what I give them. In addition there are bags and bags of wood chippings to maintain the allotment paths, and chunkier wood for bonfires.
    The composting is probably quite anaerobic due to the need to maintain the heaps in a confined space and so keep them quite compressed. None the less it is all good stuff – or at least the plants it feeds think so.
    This is just a tiny tiny part of our city, so I cannot imagine what it would be like if everyone practised this approach. Here in Sheffield most food and garden ‘waste’ goes in the bin and is incinerated. OK, we get combined heat and power, but what a waste!

    1. Thanks Gordon, that’s a good example of circular thinking within a defined area. We do something very similar. I have a wormery outside the back door, and food scraps go in there. That’s quick and high quality compost that provides for the pots, while two more conventional compost bins deal with garden waste and serve the raised beds.

      I have three fruit trees in our similarly sized mid-terrace garden. When I prune them at the end of the season I strip the leaves off the cut branches and put them in the compost, then I dry the pruned sticks and use them on the rocket stove.

      I wonder if there are intermediate ways to do this too – in between individual households and the council running town-wide initiatives. What if a waste was composted at t local park or golf course? Or food waste was collected from a couple of streets and used for biogas hot water at a nearby hotel? That’s where the best solutions may be, and we don’t hear much about those sorts of projects.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.

%d bloggers like this: