Whoever would have thought people could get excited over sewage? Well they are, in Rothamsted, in South-East England, where trials of a new waste-management process are about to begin.Normally, sewage treatment is a significant source of greenhouse gases, and so contributes to global warming. Sewage waste is usually incinerated, creating carbon emissions, and the resulting ash is used in the building industry.
A new process, that results in the creation of something called biochar, could change all this. The creation of prevents escape gases from going into the atmosphere; instead they are actually used to drive the process of treatment itself, and the product can also improve soil structure and water retention, and make soil more attractive to worms. This has been shown in Australia, the US, and Germany, where it has been found that the honeycomb structure of biochar helps to create a reservoir for moisture and fertilisers, thus cutting demand for the carbon-intensive soil treatments, and improving farm productivity.
In the sewage treatment process, a conveyor belt conveys a stream of drying effluent into a cooker where it is cooked, using gases that have actually been generated from cooking. Once cooked, what emerges is charcoal, with the carbon locked in - carbon that would otherwise have gone into the rest of the environment. This charcoal is then buried in the ground to prevent the carbon from entering the atmosphere for a projected 1,000 years or more.
Those who work with the technology are so excited by it that they want it included in the next global climate agreement, backed by activists, concerned about climate change.
At Bingen, the design engineer for the biochar plant, Helmut Gerber, originally created the pyrolysis equipment to help solve the problem of ash from sewage waste choking conventional boilers. Now, 10% of the sewage stream is diverted to the pyrolysis plant, where it is heated using very little oxygen, and where carbon monoxide and methane are burned to heat the pyrolysis process. This also results in lower fuel costs and less carbon emissions from the sewage treatment process. Mr Gerber thinks that it is possible that around 60% of the sewage carbon is locked into the char. This also helps to neutralise the removal of carbon dioxide from the atmosphere - the removal that the plants that go to create the bio-mass were originally responsible for. So the whole process is 'carbon negative.'
Some bio-char points: Making the technology affordable could be difficult. Moreover, current systems do not reward carbon storage, but rather the production of energy from biomass and waste. Biochar would need clear global incentives. However, these might be provided by the fact that, as Professor David Manning at Newcastle University, believes, that devleoped correctly, biochar could lock up as much carbon as the amount that is generated by aviation.
Biochar attracts worms. It captures nutrients that would otherwise disappear in water run-off, reducing the need for carbon-intense soil treatments or fertilisers.
Research at Cornell University in New York, US, seems to show that burying biochar can double the soil's storage of organic carbon, whereas compost releases its carbon in a relatively short period of time.
Australian research shows that biochar can reduce nitrous oxide emissions from soil. Nitrous oxide is a very powerful greenhouse gas. At the University of Bayreuth, Germany, Dr Bruno Glaser says that research suggests that biochar could double plant growth in poor soils.
Research on biochar began back in 1947. But this has been forgotten until the 1980s. Now there is a lot of excitement about what biochar can achieve.
Paul and Karen Cairns, owners of national UK skip hire company, SkipsForYou, have said that they are keen to tell people as much as they can about initiatives like this - given the recent landfill tax hike, they want to see not only their sub-contractors understanding how best to reduce landfill, but also spread the word to a wider audience.
0 comments:
Post a Comment