Diary of an Eco-Builder

The 'flush and forget' has enabled millions to deny they have a gut

Although I am desperate for our build to start going upwards, this week site foreman Steve was again going in the other direction. Directly under our tree, at the front of the site, he was putting the finishing touches to the manhole, our private entrance to that least cherished domestic environment, the drain. The tree does not have a drainpipe but deals with its wastes either by packing them into its trunk or by shedding leaves for the creatures below to consume and transform into new nutrients. Although we are following this example by designing recycling into the heart of Tree House, we're not pursuing the principle to its logical conclusion. We will not, I'm afraid, be installing a compost toilet.

Although I am desperate for our build to start going upwards, this week site foreman Steve was again going in the other direction. Directly under our tree, at the front of the site, he was putting the finishing touches to the manhole, our private entrance to that least cherished domestic environment, the drain. The tree does not have a drainpipe but deals with its wastes either by packing them into its trunk or by shedding leaves for the creatures below to consume and transform into new nutrients. Although we are following this example by designing recycling into the heart of Tree House, we're not pursuing the principle to its logical conclusion. We will not, I'm afraid, be installing a compost toilet.

Compost toilets come in many shapes and sizes, everything from "bucket loos" to special digesters in your basement. One way or another they turn your personal organic wastes into something you can sprinkle on the garden. They can be invaluable in areas where connection to a sewer is difficult or impossible, but they have an obvious downside that will always limit their ecological impact. For example, toilet flushing is the single biggest cause of water consumption in homes and compost toilets can reduce this by 100 per cent, but because your waste stays with you such toilets will only ever be acceptable to around 1 per cent of the population of Clapham. Our Ifö toilets reduce water consumption by 50 per cent but are 100 per cent acceptable. It's obvious which technology has the greatest water-saving potential.

Arguably, this mealy-mouthed arithmetic simply reflects a greater malaise. After all, high density societies have thrived with wholly localised nutrient recycling. The WC is one of the dubious pillars of modernity: the "flush and forget" has enabled millions to deny that they have a gut. And our many out-of-sight toxic waste streams may be an extension of our contemp-orary failure to confront our own shit.

Perhaps. But I'm still not persuaded by the urban compost loo. Given that our end products are 90 per cent water, the amount of compost a household can generate is fairly meagre. In cities it makes more ecological sense to deal with this at a collective level, turning sewage sludge into a renewable fuel or an agricultural fertiliser.

If you want to cut the ecological costs of your drainage, there's plenty you can do without giving up your porcelain throne. Cut your water consumption with efficient loos ( www.greenbuildingstore.co.uk), high-quality taps ( www.hansgrohe.co.uk) and efficient washing machines ( www.aeg.co.uk). Use recycled toilet paper which disintegrates quickly and won't block drains. Use toiletries and detergents that are not stuffed with nasty chemicals ( www.greenshop.co.uk). If you're doing DIY, make sure the paints and finishes you wash off your brushes are non-toxic and water-based. If you've got a compost heap, improve your personal recycling by adding your own liquid fertiliser.

If, however, you are in a location or frame of mind where an alternative toilet might be attractive, you have lots of choices. For more information, see the Centre for Alternative Technology's books Lifting the Lid and Sewage Solutions: Answering the Call of Nature ( www.cat.org.uk). For more eco-building ideas, check out the Homes for Good exhibition at the Matford Centre in Exeter this Friday and Saturday (http://h4g.sustainablehousing.org.uk).