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Tad Patzek, who along with David Pimentel has been a scourge of airy-fairy ethanol schemes, does an interview.
“Okay, grass, we are going to cut you every year, year after year. Remove everything that we cut and burn it elsewhere.” Unfortunately, when you do so not only do you remove carbon, but you remove nutrients with the grass and these nutrients are gradually depleted from the soil and of course the whole system stops producing. There is a fundamental problem with removing all biomass from an ecosystem because that ecosystem stops functioning and in order for you to make it function, you have to resupply it back with the nutrients and that of course takes an enormous amount of fossil fuels. So we are back to square one.This is a basic problem with many of the cellulosic ethanol schemes that tout the productivity of grasses with low fertility requirements compared to highly domesticated grasses such as maize. The time it takes to exhaust the soil varies depending on initial conditions, but it will always occur.
One way or another whatever is removed must be replaced or there will be monotonic degradation of the land over time. Carbon can be replenished from air. Nitrogen can be acquired that way as well, especially in symbiosis with some bacteria, though that isn't the only source. There are some algae that fix nitrogen and some comes in rain. Minerals can be replenished by dust storms and floods and so replace some of the other primary and secondary nutrients needed for plant life, but few places can be sustained this way. Minerals are mostly mined from the subsoil by deep rooted plants, or are carried to the surface by burrowing critters.
An anecdote for perspective may help clarify the issue. Growers, including graziers like me, calculate how much fertilizer we need - which includes all of the minerals not just the 3 primary nutrients - by estimating how much we intend to remove in a crop. That's what we have to pay back to the soil to stay even, though in practice we often wish to improve the soil and so pay for more than we use.
Not all growers think quite this way, and few put it in such stark terms. But a grower that doesn't think explicitly about the manganese in the manure he is spreading still has some fuzzy notion that he is providing complex inputs that have lots of good stuff. Even when the ideas are purely metaphorical, even spiritual or supernatural, there is still a type of tacit understanding about the need to return what has been taken, or there will be consequences.
You can get away with stealing from the land, mining its minerals, for a while. You may see some drop off in volume or quality, you may be able to compensate for a while, you may be able to take the productivity hit and still make out. But eventually you will be caught and punished. There's no free lunch, though payment is made on the honor system. You can cheat for a while, until lunch is no longer provided.
This all feeds into my support for farm scale pyrolysis systems. Biomass is processed to get the hydrocarbons - the easy and abundant stuff - but the residue containing biochar and minerals is retained as a soil amendment that more than compensates for what was removed since it improves soil structure and chemistry in ways that accelerate life. The syngas can be further processed to make fuel, fertilizer, plastics, or whatever. It can even just be burned to drive turbines for electrical generation, or even heat your barbecue grill :-)
Similarly, forest managers could deal with slash from felling operations and fire abatement with local pyrolysis systems. Orchards and vineyards generate woody biomass too. Cities generate lots of such materials. In all these cases the biomass is a management problem now, but it could become a valuable management tool and a profit center rather than a cost.
When all of this is added up it won't provide the volume of liquid fuel dreamed of by ethanol advocates, but it will improve all of these systems and generate some liquid fuel - or fertilizer or whatever - and so replace some amount of fossil fuel use. It could, for example, provide the fuel, fertilizer and power needs of the farming operation that produced the biomass, and so not require fossil inputs to continuing operations. Or it might help reduce the fossil footprint of cities.
The kicker is that the biochar also durably sequesters carbon drawn down from the atmosphere. If climate change due to emissions turns out to be as great a concern as many claim then this becomes a very significant attribute of pyrolysis systems. But even if it's all a false alarm it is a smart way to go since it improves the agronomic systems, producing more benefits than costs.
At some point folks like Craig Venter will perfect their engineered bacteria that eat CO2 and water and poop out gasoline, solving both our liquid fuel needs and cleaning carbon from the air. Biochar systems will still make sense. They continuously improve the soil as well as providing useful gases.
Back40's Biochar views are shared by NASA's James Hansen, in his new paper on GW Solutions the soil/Biochar get top billing.
Posted by: Erich J. Knight at May 28, 2008 09:07 PMWell, kind of. But I'm coming at it from a different place. Improving soil is a good thing - arguably a critical thing - whether there is climate change or not, whether we address that threat some other way - such as by improved energy systems - or not.
Finding myself on the same page as Hansen does not comfort me. He does not seem to be a sensible or admirable human. Let me put some distance between us.
I do find it compelling that increasing soil carbon is good for the old planet in multiple ways. It improves the soil's use of limited and expensive nutrients, including water the sometimes overlooked nutrient. That this also helps maintain atmospheric composition at levels that we are accustomed to is a secondary confirmation that this is a good direction to move.
However, it may be that simply avoiding tillage would do more for the soil and the atmosphere since so much carbon, in multiple forms, is lost due to outgassing when land is tilled. It accelerates decomposition of organic carbon in the soil, in effect speeding up the carbon cycle.
We could do both: reduce tillage and increase char amendment. We certainly do need to get very much better at this ag stuff.
Posted by: back40 at May 28, 2008 09:56 PM"Constraining past methane emissions
Although researchers know that the concentration of methane fluctuated
widely in the past, they are still unsure about the processes that drove those
changes. Now, Hubertus Fischer of the Alfred Wegener Institute for Polar and
Marine Research in Bremerhaven, Germany, and colleagues have measured carbon
isotope ratios in methane from the whole of the last glacial-interglacial
transition (between 20,000 and 10,000 years before present) by analysing ice-cores.
The results place constraints on the strength of some of the most important
methane sources, which could help improve understanding of the atmosphere's
oxidative capacity.
_http://environmentalresearchweb.org/cws/article/research/33994_
(http://environmentalresearchweb.org/cws/article/research/33994)
"
Dr.Ruddiman at UVA also uses carbon isotopic composition of Methane
measurements during the last 10,000 years of the agriculture revolution to show the
methane emission spike produced 6,000 years ago with the development of rice
patty farming. His work connects the dots of the consequences that
agricultural has had in mining carbon from the soil and anthropogenic global warming.
I like the logical thrust Dr. Ruddiman's work provides for putting carbon
back to the soil.
It makes implementing Terra Preta soil technology like an act of penitence,
a returning of the misplaced carbon.
Energy, the carbon cycle and greenhouse gas management
_http://www.computare.org/Support%20documents/Fora%20Input/CCC2006/Energy%20Pa
per%2006_05.htm_
(http://www.computare.org/Support%20documents/Fora%20Input/CCC2006/Energy%20Paper%2006_05.htm)
Erich J. Knight
1047 Dave Berry Rd.
McGaheysville, VA. 22840
540-289-9750
shengar at aol.com
I think that Ruddiman overlooks the main source of atmospheric methane: compost. Nearly every bit of organic matter produced dies, rots and returns to the atmosphere. That's just the cycle. The urge to name point sources can mislead. Wetlands, for example, may be large point sources, but most methane is emitted from non-point sources, just normal decay in anaerobic conditions, and that happens all over the planet since the bacteria that do the work and emit the methane are ubiquitous.
Agriculture complicates this picture a bit by adding some point sources, such as rice paddies, but those paddies often replaced natural wetlands. Other wetlands were drained to allow cropping. It's not clear to me what net change occured.
Emissions from dryland tillage are harder to pin point, but likely add up to larger net emissions. There is empirical support from the work of Rattan Lal which quantifies such emissions, and there is also the observable effects on soil: it loses organic matter when tilled. The change can easily be seen with no more sophisticated instruments than eyes, though there is some calibration required.
It can be argued that it is better from an emissions standpoint to burn biomass than to let it rot. Though more CO2 is produced there is less methane emitted.
Compared to combustion in a controlled boiler, open burning entails poor combustion conditions, and gives rise to significant emissions of carbon in reduced form (methane and hydrocarbons). This elevates the greenhouse-gas potency of the emissions. Biomass burial in a landfill or agricultural field leads to even greater emissions of reduced carbon than open burning.
Emissions aren't the only important issue to consider, and that's a point I think is important to make again and again. It's why I disrespect activists like Hansen. Soil needs organic matter, even if it ends up emitting more methane. It supports the ecology of the soil. It's food. The main reason to oppose tillage isn't that it causes huge emissions, it's that it kills the soil, starves soil life of organic matter. Those who are hung up about emissions may pay attention at long last when they hear that tillage causes emissions, but their hang ups aren't the real issue.
Happily, there is a way to treat the soil well while soothing the hang ups of emissions nutters: biochar. It returns carbon to the soil in a far more durable form - sequesters it in effect. Depending on the specific system used it can have even fewer net emissions than controlled bioenergy combustion. And when used in non-tillage systems there is also an increase in non-chared organic matter. It will rot and return to the atmosphere comparatively quickly, but the increase in the size of the working set in the soil means less net carbon in the atmosphere at any given time.
I'm not sure my point is clear Erich, but I'm arguing that the focus should be on soil health rather than atmospheric health. The atmosphere will improve as a secondary benefit, but the reverse is not true: soil does not improve as a secondary benefit of a main focus on the atmosphere. Indeed, many of the narrow focus proposals dramatically reduce soil health. It's backwards and has less net benefit to the system as a whole. We need to manage the whole system, not just one politically attractive aspect of it. Avoiding climate burn but starving to death is no help. We're still dead.
Posted by: back40 at June 1, 2008 10:21 PM