Composting wood releases heat. The same amount of heat as burning the wood does. However, during the composting process, the wood is decomposed by bacteria and fungi. The subsequently released energy can be used as a heat source. But the process of decomposition is slow. How can we speed it up?
By adding urine to the mix. Chinese researcher Shiyang Fan obtained his PhD on a study of this effect. The key element is nitrogen. Micro-organisms require nitrogen to grow. Wood is rich in carbon but contains very little nitrogen. Adding nitrogen boosts the wood’s decomposing process.
Using urine to boost the decomposition of wood reduces pressure on the sewage purification systemsShiyang Fan, researcher Environmental Technology
In his experiments, Fan reached a seven-fold faster decomposition process. ‘Fast’, however, is a relative term. He monitored the process by measuring the loss in the wood’s weight and how much oxygen was used in the process. Over a 42-day period, the wood’s mass decreased by one fifth, almost seven times as much as without the addition of urine.
There are several reasons to use urine. ‘Urine is a waste product, but it is rich in the nutrients nitrogen, phosphor and potassium’, Fan says. ‘Urine is also known as liquid gold. Reusing it is important. Moreover, using urine to boost the decomposition of wood reduces pressure on the sewage purification systems.’
Gaining heat from compost, also known as thermal heat, is not new—the Dutch Biomeiler foundation experiments with this method. Fan’s attempts to accelerate the process are the next step. Fan says that composting may well be a promising and sustainable alternative to incinerating wood. The sustainability aspect lies in the residue.
Not all of the wood disappears during the composting process. What is left behind is a peat-like mulch, which can be used as a soil enhancer. A major drawback of this method is the time it takes. With or without urine, fire is faster.