May 26, 2008
Tad Patzek Interview On Biomass Energy Problems

The Oil Drum: Canada has an interesting interview with Tad Patzek, a professor of civil and environmental engineering at UC Berkeley, about biomass energy sources. Patzek publishes research on the energy return on energy invested for biomass ethanol sources. In this latest interview many topics are covered. The most interesting to me was Patzek's view that biomass energy isn't sustainable because it drains the soil of minerals.

Ben: So, we have identified that the largest energy input is the actual industrial process. People are moving away from natural gas to coal power now because the price of natural gas is too volatile. What if we started burning biomass instead of coal because biomass, some types of biomass such as pelletized switchgrass for instance has a fairly good energy balance, does it not, when you burn it.

Tad Patzek: Right. So here we are running into another problem. The thing about agricultural production is that it requires a substrate. Plants need soil to grow on and that soil needs to be protected from the elements, wind and rain being the most important ones. So a prairie system with switchgrass let us say protects the soil very well because the soil is covered with plants all the time. Prairie in fact is a very good example of a system, which is enormously efficient and whose net productivity, that is, net mass production is zero. That is, everything that the prairie produces is recycled in it. The bison, the buffalo eat the grass. The coyotes and the lions, mountain lions, eat the buffalo, and the wolves and everybody dies on the prairie and their bodies are recycled and so it goes on, the nutrients, and in fact the prairie gets flooded every now and then from the rivers, which bring other nutrients and so it goes on, the nutrients are resupplited. Now we come, we the humans come into that system and we say, “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.

Using cellulosic technology to extract energy from plant matter such as switch grass will be even worse for the soil than corn ethanol in this view because a larger percentage of the plant matter will get removed during harvesting. The concentration of minerals in corn kernels (which are mostly starch) is lower than the concentration of minerals in corn stalks or in grasses.

Patzek sees a similar problem with use of sugarcane in Brazil to produce biomass energy. Such farming will deplete the soil faster because more of the plant will get removed from the farm for processing.

Tad Patzek: Sugarcane has another feature that differentiates it from corn. It actually coexists with a bacterium, Rhizobium bacterium, to some extent, which sequestered nitrogen. So sugarcane needs less nitrogen fertilizer than corn. Also, it grows year around not 100 days per year as corn does in the United States. There are differences in the yield. Also, sugarcane in the past centuries was grown organically with no fertilizers and basically what was taken out of the plantation in the end was the sugar juice, the carbon, in terms of sugar, but the rest of it and some fiber from the bagasse, but the rest of it would be returned back to the plantation as malt and as fertilizer and that would actually allow these plantations to go on for three centuries in some places.

Ben: Okay.

Tad Patzek: In Asia and in South America, so very good so far. Now, we are now doing it slightly differently. Now, in order for us to drive the process with sugarcane only, we need to use the entire plant, that is, the bagasse, the leaves and everything else and essentially bury them in the ethanol plants. So now we are removing all biomass from the fields. Of course, that puts us in the quandary that no we will have to be replacing the nutrients just as we do with corn. In Brazil, this is not being done to the same extent yet. So they are essentially depleting the soil and unfortunately they will have to do more and more fertilization as they go on with the system.

My expectation is that very low cost photovoltaics will eventually make an acre of desert capable of producing electrical energy from photovoltaics much more cheaply than an acre of farm land will produce biomass energy. But the electricity won't be as convenient to store and use as are liquid fuels. Better batteries will improve the usefulness of electricity in transportation. But liquid fuels will still provide advantages - especially for longer trips. So even with super cheap photovoltaics I still expect some political demand and economic demand for biomass liquid energy, enough to do a lot of environmental damage.

I think government support for biomass energy is a measure of both the corruption and relative stupidity of our elected officials. That, in turn, is evidence of two problems. First off, the average voter isn't bright. Second, the average voter has little incentive to be well informed about what elected officials believe and do.

Share |      Randall Parker, 2008 May 26 05:05 PM  Energy Biomass

Fly said at May 26, 2008 6:44 PM:

"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 don't remove "all biomass". Just remove fuel which is carbon, hydrogen, and oxygen, burn the waste biomass for energy, and return the ash to the fields. The only inputs needed are carbon dioxide, water, and light. Bioengineer the fuel producing plants to support the necessary nitrogen-fixing bacteria. Minerals only need to be replaced if irrigation causes accelerated mineral depletion by runoff water. If soil is depleted during sugarcane production the problem will be fixed without requiring "enormous amount of fossil fuels".

(A bigger problem would be if farming increase the concentration of harmful minerals in the soil. E.g., irrigation water might deposit salt into the soil faster than it carries it away.)

Randall Parker said at May 26, 2008 6:54 PM:


The biomass gets trucked away to processing plants. Only at the processing plant does the hydrogen and carbon get separated.

Wolf-Dog said at May 26, 2008 8:05 PM:

Although it is true that harvesting and removing the biomass obviously takes away minerals from the soil, if and when the ashes of the burnt biomass are returned back to the same land, the cycle becomes complete. This is overlooked in the interview. Apparently in this article it is assumed that the ashes will not be brought back to the place of harvest. In fact, the switchgrass and wood that is burned in power plants, will leave a lot of pure ash, which contains all the minerals that were stolen from the soil. If the same ashes are returned back to the soil, then there will be a perfect cycle. The minerals do not evaporate, only the carbon evaporates when it is burned, and that carbon comes from the atmosphere. Although the ashes that result from burning coal, are very heavy and clumsy to carry all the way back to the coal mines, the ashes of burnt biomass would be very light and compact, and hence quite easy to bring back to the place where the biomass was harvested originally.

Wolf-Dog said at May 26, 2008 8:08 PM:

This article also overlooks the possibility of algae farming, which would not need minerals because once the oil is extracted from the algae, the remainder of the algae can be returned back to the same pool immediately. Algae often contain more than 50 % oil, and this makes it far more efficient in terms of surface area.

Blyte said at May 27, 2008 2:44 AM:

Patzek refers to "the nutrients" as if talking about a mystical entity. Garbage. Literally, the recycling of garbage is the key. Nitrogen can be fixed from the air. Other "nutrients" can be cycled in from agricultural and industrial processes. Manure. Byproducts of chemical processing. Etc. What makes soil special is its microbial content. Depleted soil can be rejuvenated. Genetic engineering is the key to better nutrient cycles.

What do they teach in environmental engineering school? How to be a "consultant?"

Allan said at May 27, 2008 5:30 AM:

Blyte is right. I've taken poor soil and rejuvenated it thru simple composting. Based on his logic we shouldn't be farming either. Nonsense.

RP said at May 27, 2008 6:50 AM:

Too much reading of will cause you to leap from a bridge. People come to believe what others around them believe. While the articles on that site are often very good, most of the comments come from misanthropes who are literally praying for the collapse of civilization, and slobbering at the thought of worldwide human misery. Any possible solution to our energy problems that anyone puts forward is immediately shot down because it disturbs their vision of some bucolic pre-industrial utopia.

Kent Gatewood said at May 27, 2008 7:59 AM:

How do hay farmers deal with mineral depletion? Straight question from a city boy whose country grandparents would be appalled at my ignorance of the farm and ranch.

Randall Parker said at May 27, 2008 8:07 AM:


The comments are far worse than the posts at The Oil Drum. But I'm quoting from a post.

I do not expect (and have argued there) that we will revert to a pre-industrial society. Not all their posters do either. I wouldn't call Stuart Staniford as apocalyptic either and I've quoted him on this topic.


Composting requires larger quantities of materials. Farmers prefer commercial chemical fertilizers because they can work with a couple of orders of magnitude less stuff.

Maybe some types of biomass processing plants can produce residue that has high mineral concentrations.

My biggest problem with biomass energy (with the possible exception of algae) is that it requires far too much land.

Brett Bellmore said at May 27, 2008 8:39 AM:

"How do hay farmers deal with mineral depletion? Straight question from a city boy whose country grandparents would be appalled at my ignorance of the farm and ranch."

Locally? They test the soil periodically, and then spread the appropriate materials over their fields. It's not like the depleted minerals are expensive, or required in huge quantities. I do hear that soil mineral depletion was once a serious problem for primitive farming cultures.

aa2 said at May 27, 2008 12:52 PM:

Biomass for energy was big in the pre-coal days.. Burning wood and other biomass for heat, cooking, forging etc..

Anyone who supports biomass energy today doesn't understand scale.

Lorne said at May 27, 2008 1:02 PM:

A crop of primarily grass hay requires the application of approximately 200 pounds of urea nitrogen fertilizer 46-0-0 every year (100 lbs of actual N) assuming reasonable rainfall and crop growth. It requires a third to a half that amount of phosphate, sulphur and in some cases potassium also to keep up production. If you are not applying that amount of fertilizer you are mining carbon from the soil's organic matter and production will drop as as carbon in the organic matter is depleted. Currently nitrogen fertilizer is selling for $800 a tonne (tonne = 2200 lbs) , phosphate is selling for $1400 a tonne. Alfalfa and other legume hays produce their own nitrogen but still need the other nutrients.

The difference between hay (or biomasse) and grain production, as is stated in the interview, is that only the grain is removed from the field in crop production. The only thing left behind in biomass or hay is the roots. MInd you have a plants organic mass is in its roots.

I have often thought that many of the scenarios promoting switch grass and other grasses like this were just technicolor dreams. They assume that crop residue is of no value to farmers and that they will line up to get rid of it. This is just nuts. Remove all the tilth and the soil becomes as unworkable as asphalt. It also seems to be assumed that switchgrass can be grown and harvested for almost nothing. Any time you see some one advocating switchgrass, but valuing it at less than $60 -$70 a tonne at the farm, you can assume they are fudging numbers. No one would cut and bale it for less.

By the way when diesel fuel is selling for $5.00 a US gallon who would pay for hauling the ash back and spreading it on the fields as some here advocate? Patzek's comments are 100% accurate. The only cellulosic ethanol plants that will ever be built are ones that use forestry waste. None of the others will ever be financially viable because of logistic costs of hauling vast amounts of biomass to the plants.

Larry said at May 27, 2008 2:36 PM:

WolfDog has it right. Desert-grown algae will produce much higher energy out for resources in than other biomass. It doesn't depend on soil quality, only on water quality and sun. Algae is in a race with PV for future energy resources. The battle is being fought on scalability and cost.

Nuclear fission and polywell fusion are also possibilities if the former can lower its costs and the latter can be made to work.

Short-term, it's all about the negawatts...

Bruger said at May 28, 2008 9:40 AM:

Wrong. Scientists are developing nitrogen fixing strains of wild grass even as your grubby fingers hit the keyboard. No need for urea fertilizer. Cheap and plentiful sources of other nutrients are being developed even as you wrinkle your eybrows in surprise, from manure and other farm and forestry waste. It's a new world, farmer, and you'd better get with the program.

Wolf_Dog said at May 28, 2008 1:33 PM:

Some say that sending back the burnt ashes back to the biomass farms is too expensive. It seems that they are confusing the biomass ash with coal ash. The biomass ash (if burned properly), is much lighter than coal ash. This makes a big difference. Hence it is probably not too expensive to carry back the biomass ash back to the farms.

Ken said at May 28, 2008 5:18 PM:

Soil loss and depletion is an ongoing issue for agriculture, not limited to biofuels. The loss of arable land in Australia has been enormous, and whilst practices have improved, it only takes a drought to undo years of effort - or a big debt to persuade farmers it's better to grow a quick crop in the cheapest easiest way, and put off improvements till there's been a couple of good seasons. I doubt the situation is much different in the US. Having abundant cheap fuel helps. Not having abundant cheap fuel won't help.

Bob W said at May 28, 2008 8:50 PM:


If you have found a way to make a grass fix nitrogen you better patent it call Monsanto, Syngenta, and Dupont and start a bidding war. You are going to be richer than Bill Gates. You've just found the Holy Grail of crop breeding. No more having to add nitrogen to corn, wheat, sorghum and rice. You will have personally solved the worlds grain shortage, eliminated the fertilizer dead zone in the Gulf of Mexico and will likely get a Nobel Prize to boot.

Randall Parker said at May 28, 2008 9:43 PM:


I reported on those efforts to develop nitrogen-fixing strains of grain crops years ago. We are still waiting for those scientists to succeed. Do you have specific reasons to expect success in a few years? I'm expecting longer than that.


I didn't know that Syngenta was working on the problem too. Thanks for mentioning that. But Syngenta's web site isn't specific on just what they are doing with nitrogen metabolism in corn. They are doing something. But maybe not fixation of hydrogen to nitrogen.

Monsanto seems like they are trying pretty hard to come up with a solution. Maybe Evogene came up with some useful genes toward this end.

ST. LOUIS, MO and REHOVOT, ISRAEL--(MARKET WIRE)--Sep 25, 2007 -- Monsanto Company (NYSE:MON - News) and Evogene Ltd. (Tel Aviv:EVGN.TA - News) today announced a collaboration to improve nitrogen use efficiency in corn, soybeans, canola and cotton. Under the agreement, Monsanto gains exclusive rights to a number of genes discovered by Evogene that help plants maintain yield with lower applications of nitrogen. Monsanto will work to evaluate the use of those genes in its research and development pipeline. The potential candidates from Evogene are complementary to the nitrogen utilization genes already in testing in Monsanto's pipeline and could provide the opportunity to further a series of upgrades for this key target area. The financial terms of the agreement were not disclosed.

But these genes sound like they are aimed at nitrogen handling efficiency, not binding of hydrogen to nitrogen. I think the binding problem will be hard. Will they take genes from microbes and put them into corn and wheat so that the whole microbe compatibility problem doesn't have to be solved?

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