Compost Toilet in a South London home

Donnachadh McCarthy is not just your average environmentally aware person. He runs an eco-auditing business and his home became the first carbon negative home in London in 2006 – not bad for a victorian terrace!

Donnachadh's Camberwell Eco House

His home boasts solar electricity, solar hot water, a wind turbine, a wood burner, solid wall insulation, a rain harvester and now, a compost loo!

Whilst understanding the potential benefits of a compost toilet, Donnachadh was initially reluctant to pursue the idea, initially opting for a system of collecting rain water which would then be used to flush a regular toilet. Whilst this is a massive improvement over using mains (fresh, drinking quality!) water, your personal waste is still being flushed ‘away’ and the processing of it, back to clean drinking water is very energy intensive.

Donnachadh by the rain harvester
The rain harvester on the side roof at of Donnachadh’s house. This provides the flush water for a conventional toilet.

Ever mindful of reducing his carbon footprint still further, in late 2012 Donnachadh took the plunge and bought a Separett Privy 501 urine-separating dry composting toilet kit from us. With the help of some friends, he collected waste wood and the other bits needed to install it and in a short time it was ready for use in his bathroom. Using an old builders bucket for the solid ‘waste’, a simple framework and top was constructed of recycled wood around the Privy 501. Pee goes into re-used 5 litre-washing up liquid plastic-container and is emptied onto compost heap (it’s a great activator). Finally, a vintage ‘Hovis’ tea-towel offers a simple ‘modesty’ panel covering the bucket which enables easy removal for composting.

Guests have the option of using the ‘standard’ toilet if they prefer, but it shares the same space as the compost loo, which Donnachadh was pleased to report does not smell! For odour control, Donnachadh uses a handful of cover material (old newspaper, wood ash and sawdust – all free!) after each visit – this acts as a physical barrier to keep smells down to a minimum (separating the urine means the feces does not smell as bad as you might think!) and also helps to balance the compost mixture.

When the solids bucket is full, it’s emptied onto a dedicated ‘humanure’ compost heap in the garden, where it’s left to compost down to a safe and pleasant smelling compost which will be used around his suburban garden to help grow fruit trees, herbs and other crops, helping to close the fertility loop!

Donnachadh McCarthy FRSA

Donnachadh McCarthyMedia- environmentalist, environmental journalist, author, broadcaster, home and business eco-auditor.

Donnachadh is the founder of the national award winning eco-auditing consultancy 3 Acorns Eco-audits which provides eco-audits to private homes, schools, charities and businesses.

His clients have ranged from homes and schools all over Britain to the HQ for Novartis, Brunswick Group and Good Energy in the corporate sector.

His home in Camberwell has solar electricity, solar hot water, a wind-turbine, a wood burner composting-loo, solid wall insulation and a rain-harvester.

In June 2006, his home became the first home in London to actually become carbon negative, i.e. he exported more green energy to the national grid than he imported fossil fuels over the previous 12 months. It produces less than half a wheelie bin of rubbish per year and uses about a fifth of the average London mains water consumption.

His home won the National Energy Efficiency Award in 2008 and the London Marchant Award in 2009.

Donnachadh ran the innovative charity eco-auditing project for the City Bridge Trust which won a Green Apple Award in 2007.

Donnachadh McCarthy was the eco-auditor on the hit BBC2 series “It Is Not Easy Being Green”, ITV’s “How Green is Your House” and Sky’s “Green Britain Week”.

He is a freelance environmental journalist writing for The Independent and The Guardian and is author of “Saving the Planet Without Costing The Earth” and “Easy Eco-auditing” which is a guide to home and office eco-auditing. He is currently working on his new book “The Prostitute State” on how the corporate capture of our political systems is damaging our attempts to save the planet.


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