Dry toilet systems abound, but are usually dependent on relatively low loading. They are also quite expensive, and don’t work well when used inappropriately (i.e. putting non-biological effluent down them). However, they work very well when combined with a composting system and provide a cyclical approach to nutrients without relying on extensive water use. Perhaps most importantly, once the effluent has been digested by bacteria in the sump, it is sterile and can be used for fertiliser or fuel – potentially even providing a source of income.
Bio-digesters are vessels which generate biogas through the bacterial digestion of organic waste. Industrial scale systems are typically aligned with pig farms, but again the potential exists for small or medium scale systems to be linked with municipal sanitation services. Again, the ‘waste’ becomes a resource for the generation of energy.
Moving on from the technology though, the engagement of end-users is essential, and civil society has an important role to play. Communities in Cape Town have rejected dry-toilet systems as inferior – an understandable viewpoint given the ‘aspirational’ nature of a white, porcelain, flushing loo. But I wonder if there were an income stream from the provision of sewage (as fertilizer to a community garden or as feedstock to a bio-digester operator) whether those perceptions could be shifted.
Based on what I have seen in successful strategies for renewable energy in informal entitlements in India using micro-finance (like Pollinate Energy), I am convinced appropriate solutions for sanitation can be found, with sufficient humility and willingness to engage.
I haven’t done the design work and I’m not a waste-water specialist, but I have been seen a wide range of design processes that challenge the status quo, and the options are always wider than we first imagine.
I believe a first step for Cape Town might be to get some heads around a table – World Design Capital 2014 might be a good forum to do this in. There are bio-tech specialists at UCT (and almost certainly elsewhere), world class engineers and an engaged civil society in the City. Perhaps get a facilitation specialist to manage the process – a team like Meshfield… But put experienced, innovative people around a table, with a brief and a budget and get them thinking, designing and working.
- Trial a range of dry-toilet systems aligned to community gardens (Cape Town has poor soil, so nutrients are a limitation); not as a strategy to deliver the services to all, but to showcase how the tech works.
- Do your best to secure buy-in and support from civic, health and community organisations.
- Finance some of the investment from your health budget as the payback on ‘prevention’ will always top that on ‘cure’.
- If it is possible to build a business case around the production of local food, and the stigma (and actual safety and health) of waste-to-food can be managed (which they can), then do so. Frame the venture as a business exercise for value creation from a waste product, and better health and sanitation or a by-product.
- energy neutral (i.e. powered by renewables)
- cycle water
- provide sterilised, dry sludge that can be used for fuel