Archive for Biomass

Wood gas conversion of pickups

Biofuels Digest brings us the story of Wayne Keith and his wood-syngas conversion for pickups (I get the feeling he uses mostly pickups because you can use the truck bed as you “gas tank.”

I think this option has a lot going for it. The biggest barrier to cellulosic biofuels in my mind is the dispersed nature of the resource… it’s difficult to gather it op in one place to convert it efficiently into fuel. So if the conversion is done in the vehicle, the dispersed nature of (especially rural vehicles) is a much better match for the dispersed nature of the resource.

Gasification is not a good option for urban vehicles (since the resource is relatively scarce there, although much garbage works in these trucks), but it seems an elegant solution for utilizing the large volume of diverse biomass that would never be collected by commercial operations because it is both to dispersed and varied.

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2% National Coutput -or- 10,000 Cows per MW

A commenter on my recent pro-transmission article questioned some statements of mine about the availability of renewable electricity from cow manure.  I had stated that 

  1. It was most likely baseload.
  2. There was not much of it in many states.

The first observation comes from the fact that the digester is sized so that
it runs as much as possible to produce the best economics.  Manure also
breaks down over time, and so is likely to yield more electricity if used as
quickly as possible after it’s produced.

Total Cow Output (Coutput?)

I thought it would be interesting to run some numbers and see how much
electricity might be available from cow manure.  First I had to come up
with some numbers for kWh/cowyear.  I found an example of a 50 kW engine running 14h/day on the produce of 300 cows.

That’s 850 kWh/cowyear, or about 100 W/cow, or 10,000 cows/MW.  A single cow produces enough manure to run one incandescent light bulb (or four CFLs) year round.

The US has about 100 million cattle, capable of producing 10 GW of electricity (if all the manure was gathered and processed in anaerobic digesters,) or 85 million MWh/year.  Total US Electricity production in 2007 was 4,208 million MWh, so 100% conversion of cow power into electricity could supply 2% of total US electricity.

100% conversion is a rather heroic assumption, especially for pastured cows, but I’m not including other types of livestock (pigs, chickens, etc.) so 2% of electricity seems like a reasonable potential estimate for total anaerobic digestion of manure. 

2% is actually a higher number than I would have expected, although that potential for electricity generation is unlikely to be reached, since much might be converted to liquid fuels for transport.

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Is There a Tradeoff Between Economics and the Environment?

Tom Konrad Ph.D.

California’s RETI process lends insight into the near-term prospects of Solar, Wind, Geothermal, and Biomass.  

In September, California’s Renewable Energy Transmission Initiative (RETI) released their Phase 2A report, which outlined potential transmission corridors to collect renewable energy from Competitive Renewable Energy Zones (CREZ) that had been identified in previous phases.  As part of Phase 2A, they also screened each CREZ for environmental impact, and the potential difficulty of obtaining land for renewable energy development.  

I previously looked at the results from Phase 1A and gained some insight into the cost of renewable energy technologies.  However, what renewable energy projects actually get built has to do with a lot more than just economics.  If it raises too many environmental concerns, such as infringing on endangered Mojave Ground Squirrel habitat, it isn’t going to get built.

Drawing on the spreadsheet "Supplemental Materials, CREZ Data" I put together the following charts, graphing the economics of each type of renewable energy in each CREZ against the expected environmental impact of that CREZ.  

Each circle represents one type of renewable energy at one of 35 CREZs.  Concentric circles in different colors appear where a single CREZ offers multiple types of renewable energy development.  The only difference between the two graphs is the size of the circles.  In the first graph, circle sizes represent the potential annual energy production (GWh/yr) of a CREZ, while circle sizes in the second shows power rating (MW.)  Geothermal and Biomass resources are relatively larger in the first graph because these are typically baseload technologies generating electricity near peak capacity all the time, while solar and wind are variable.

The cluster of circles in the middle right represent resources outside California: they were not rated for environmental concerns, so I assigned them an arbitrary value in the middle of the range in order to display them on the charts.

Economic/Environmental Tradeoff?

I found it surprising that there is little evidence of a tradeoff between economic viability of CREZ’s and environmental impact.  In fact, the circles in the graphs above are generally clustered along a line from the lower left (high environmental impact, bad economics) to the upper right (little environmental impact, good economics).  A tradeoff between economic viability and environmental concerns would manifest itself in a clustering along a line from the upper left (bad economics, little environmental impact) to the lower right (good economics, large environmental impact.)

Considering these four major renewable energy technologies, as they might be deployed in California, there is no real tradeoff between economics and the environment.  The best economics coincide with the least environmental impact.  If we were to include energy efficiency in the analysis, the trend would be even more pronounced: energy efficiency has the best economic profile of all, yet avoids the use of energy and hence does less harm to the environment.

The exception here is biomass.  The small green dots don’t show a pronounced trend in any direction, meaning that there may be some tradeoff for biomass.  Such a tradeoff would not be surprising, because harvesting plant matter on a large scale is bound to have significant ecosystem impacts.  Note that Biomass here does not include such technologies as waste to energy, which can be environmentally benign, or even an improvement compared to land filling.  In this study, the biomass in remote regions that do not yet have transmission, since lack of sufficient transmission was one of the requirements to be a CREZ.

With clean energy, it may actually be possible to do well while doing good.

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