Almost everybody is aware of
global warming and that carbon emissions are a big issue. A
recent report by Dr. Johannes Lehman of Cornell University titled "Biochar reduces nasty nitrous oxide emissions on farms" highlights a
significant but under-reported issue and a new potential solution.
“Carbon Dioxide has a quiet but
strong partner in climate warming crime – nitrous oxide. This nasty gas is usually produced on farms
from animal manure waste and the use of synthetic fertilizer. In fact, nitrous oxide in agricultural soil
has 298 times more global warming potential than carbon dioxide.”
In an urban environment, we are
not worried about confined animal feeding operations, but we are still
contributors to nitrous oxide production.
Every compost system that is not working right (carbon to nitrogen
ratios, moisture levels, etc.,) can be contributing nitrous oxide into the
air. While each residence may be
contributing only a small amount, collectively we are responsible for a
significant quantity. Our ‘resident’
potential will continue to increase as more residents consider composting
systems and even grey water systems.
What the research team at Cornell
discovered was that no matter the soil type or the biochar type used by scientists,
a universal truth emerged: the emission
of nitrous oxide was always reduced on average by about 55 percent, compared to
benign nitrogen gas.
Microbial Earth Farms (MEF) offers a variety of products that help to
address this problem, including biochar, and even better, fermented
biochar. MEF has long been aware of the
potential for bokashi to reduce methane emissions in food scraps as well as in
chicken houses, and now when combined with biochar, we are expecting
significantly less emissions than bokashi alone. See our Bokashi Plus product. This is important because it can also extend
the life of poultry bedding and/or compost worm bedding in urban situations.
I don’t get positioning grass as a carbon source. I wouldn’t attribute a problem to grass if it is really due to the surrounding environment. I thought all green plants (corn and grass) used photosynthesis to process CO2, sequester C, and emit O2 in the process. If the urban heat increases microbial activity emitting CO2 I wouldn’t blame it on the grass! ?
ReplyDeleteIt is not clear a season corn lifecycle (seed to market) was compared to whole season of (established?) grass. Did it include the tractor fuel and fertilizer? Are the cornstalks remainders plowed under? I would want a controlled and equal environment in which to make this analysis. Should I tare-out my lawn because it is a CO2 source?
From this description I don’t believe the Elizabethtown study is good science. It seems to be telling me grass is bad because it harbors CO2 emitting microbes. A study on how to manage heat-island-grass so it isn’t a CO2 source but rather a sink would be more interesting than a comparison to corn grown in the country.
Thank goodness the NASA analysis finds that lawns are a net sink. I was amazed at the characterization that lawns are “America’s largest irrigated crop.”
David
DeleteFirst, yes, lawns will emit more CO2 than corn fields. We have been getting data on numerous soil samples for residences here in Austin. Soil respiration is a function of the organic matter and decomposition in the soil. 7 out of 9 samples we had from residential soils did not need more compost as they were already over the 4% hurdle for a sustainable soil. Many of the samples were in the 5-8% range meaning they did not need to spend money on compost - it was not the limiting step in their soils. That is not great news for a compost sales person.
Corn fields as a comparison have often had their organic matter burned off through the successive years of chemical fertilizers. Their organic matter is often down below 1%. In central Texas, we often find soil samples at less than 0.5% organic matter, or 1/10th of residential soils. Why does this matter? CO2 emissions are related to the decomposition of organic matter and microbial activity in the soil. Through the solvita test, we are able to measure this respiration rate. In this report, (I have yet to verify this), consider that they are measuring the base output of the soil, such that you might imagine a glass bowl inverted and lying on the soil to capture the emissions. Do not consider the plants produced by the soil, but that the soil is barren of plants so that emissions can be properly captured.
The real trick/consequence to this report is that there is an optimum to CO2 activity in the soil. We need to have microbial activity (link to a good USDA site on soil biology) and respiration at an optimized level. I would propose that this report is to linear in it's thinking and not nearly holistic enough to provide guidance on how to manage soil CO2 emissions and organic matter levels. An old axiom is that 'water follows carbon' and the more carbon you have in your soil, the healthier it is.
A better mental framework for this issue is to think about how we can capture more of the CO2, methane and nitrous oxides in our soil, where they can be used to increase total plant biomass. Biochar is one of the more compelling answers to this problem, as well as fermentation.
I wish that I had more time to dig deeper into the article. I was only able to look at the article summary which I linked into my blog. Thanks for the stimulating debate!