It is argued that medium-term climate change targets can not be reached if C sequestration in soils can not be increased drastically. In fact, the opposite trend is observed in many soils on a global scale - decreasing organic matter. Besides, waste disposal is steadily increasing so far in most countries (e.g. Hoornweg & Bhada-Tata, 2012). This trend is especially observed for urban areas that can be considered as final anthropogenic sinks for food waste, organic solid waste and sludge from sanitation whereas urban population will soon reach > 50% with ongoing growth trend. However, as larger the cities grow as more difficult (increasing distances, transport barriers) and costly it becomes to recover organic matter and to return it to peri-urban or rural farmlands.
...Johannes I think you may do a Life Cycle Assessment to assess this issue or even look for LCAs on that issue. However, maybe I did not understand your question. BR Nils
Hi Nils,
many Thanks for your answer. LCCA may be a suited choice to establish data for one selected city or one defined regional system. May be you are aware of a related publication? I placed my question to ask for feedback from researchers who are already working on this topic and may have ideas, methods, approaches available that could support our related research program.
Regards, Johannes
Johannes,
My Department procured a couple of projects investigating some of the logistics behind this issue in a more general sense a few years ago, which may be of interest:
http://randd.defra.gov.uk/Default.aspx?Menu=Menu&Module=More&Location=None&ProjectID=17396&FromSearch=Y&Publisher=1&SearchText=ac0409&SortString=ProjectCode&SortOrder=Asc&Paging=10#Description
http://randd.defra.gov.uk/Default.aspx?Menu=Menu&Module=More&Location=None&ProjectID=12886&FromSearch=Y&Publisher=1&SearchText=alowance&SortString=ProjectCode&SortOrder=Asc&Paging=10#Description
regards
Murray Hart
Dear Murray,
many Thanks for your feedback and support. The regarding outline of research look very interesting, unfortunately the full reports can not be downlowded from the provided links. Would you have e-copy's/pdf for me? To be send to [email protected] ?
Many Thanks for sharing and your efforts! Johannes
Dear Johannes,
there does seem to be an ongoing problem with our Science Search site at the moment. I also get a message saying the file can't be downloaded, on the first link anyway, but there should be a 'retry' button on this message, which if you click on it the file should then open. Would you mind trying again? If it still doesn't work I will email them as you requested (The second link's document is possibly too big for our email system, although I might be able to zip it to a smaller size. However, this one seemed to open OK for me, although a bit slow)
kind regards
Murray
Dear Johannes,
This sounds like an interesting project. With respect to understanding the carbon dioxide equivalent avoided or removed through urban waste projects such as landfills, you could refer to carbon offset project Project Design Documents for projects centered on waste or landfill management. The VCS has certified projects in both developing and developed countries. Best of luck.
Jayme
Dear Johannes,
This is a very interesting question. The last civilization that was somewhat successful with (accidentally) sequestering carbon in soil were the native people of the Amazon basin, if I am not mistaken. Though I do not know if the resulting Terra Preta had an impact on the climate. Today it would already be a huge success if we avoid any methane emissions from organic residues due to landfilling. It is also kind of funny when we speak about carbon offset projects in poorer countries while the industrialized nations continue to burn coal, oil, and gas in order to fill the pockets of a few absurdly rich people.
Anyway, one method to sequester carbon in soils is the carbonization of organic residues. The resulting biochar is then applied as soil conditioner. Very roughly and on average, it is possible to sequester 50% of the biomass carbon into biochar. The same applies to compost, though its carbon is not as stable as biochar. On the other side, biochar alone is not very effective and sometimes detrimental to soil fertility. It needs the combination with nutrients and microorganisms, which are plenty available in compost. Taking this aside, if we assume that we would take all plant based residues in Europe from forestry, agriculture, and settlements, around 500 Million tonnes, then the resulting biochar (conversion rate 30% with a final carbon content of 80%) would only offset 10% of the European GHG emissions (1200 Million tonnes). For poorer regions with less GHG emissions the relative offset would look better, but this European example should illustrate the limited power of biochar in terms of a short-term climate solution.
However, there are also good news. In terms of an economic implementation, it was shown that biochar can be a viable solution to increase the incomes of smallholders, while sequestering carbon as a bonus. Please take a look at the linked publication by Schmidt et al (2015). Of course, in and around cities such a model would require land rights to smallholders or smallholder cooperatives.
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