More Science with Peter

Where does all the muck go?

With the second instalment of my other blog at the Guardian and Observer, it seems pertinent to be talking about manure and related topics. At this time of year conscientious people turn their thoughts to mulching: wood chip, home-made compost, leaf mould, whatever suits. Food growers and rose growers begin to consider muck by the barrow load, carefully sourced and well-rotted. People who plan ahead know that this will serve them well in the spring, after the frost has attacked and the worms have partaken. The 'solid waste' to use a grown up term, dissolves happily but what about the bulk, the part which has not passed through anybody's digestive system? Straw and wood shavings can take much longer to break down, sometimes five years. But what do I know? Here's Peter.

'The plant material (straw etc.) contains lignin, and rain breaks it down over time,' he clarifies. 'Acid rain performs this task but the process is speeded up many hundreds of times if the water has a higher pH. The proper term for this is alkaline hydrolysis.' Dismissively, Peter adds: 'It's a long chain thing.' In anticipation of an interruption he waves his hand. 'No questions. The process shortens the lignin and it then dissolves.'

There follows quite a lot of science on rain water seeping through carboniferous limestone in the Peak District, peat lignin breaking down, resulting in tea-coloured water, perfectly good to drink 'unless it has passed over a dead sheep or similar...' But regrettably there are space constraints.

So, to answer the other pressing question, 'Where do all the leaves go?' They go to the same place as the muck. It's got something to do with alkaline hydrolysis.