Use of Sewage Sludge in Construction Gunn, Dewhurst, Giorgetti et al, CIRIA 2005. 166pp. £45 (member price)
Unfortunately, this book arrived too late for our Christmas round-up, but what do you give a man who has everything?
If you can bear the thought, this is quite an interesting book about the uses that recycled waste - waste, in the truest sense of the word - can be put to in construction materials and 'provides information for stakeholders in the recycling of sewage sludge including sludge producers'. Nice. I won't tell you what 'bloating' and 'radiative forcing' mean.
The premise of this book is what to do with the 30 per cent of the one million tonnes of sewage sludge solids that are not used in agriculture. The incorporation of sewage sludge into bricks was patented in 1889 but never caught on. In general, this refers to incinerated sludge ash, (although sludge cake can be used for cement manufacture because of recent technological advances in phosphorus recovery from the sludge, making the cement mix more stable). However, the strength of concrete reduces once the proportion of ISSA (incinerated sewage sludge ash) exceeds 5 per cent.
The Health and Safety concerns are less obvious than might be thought, with the release of dioxins and furans if the material is sawn, broken or damaged, leading to ingestion of dust particulates. The risks are tiny, although given the paranoia about health and safety in general, and dioxins in particular, this could be a contributory issue leading to the slow take-up of an innovative use of waste material. The fact that incineration is the primary action in the process cannot do the acceptance of this technique too many favours either. However, a large portion of the text is taken up examining public perceptions, toxicity tests and risk assessments.
This is very much an internal, specialist text but indicates that there are more imaginative ways of using waste, especially as concerns about the health implications of muck-spreading on agricultural land increase (it is banned in Switzerland from this year).