Biofuels: an open letter to Senator Jeff Bingaman (D, NM), from a citizen of New Mexico and a researcher on issues of global change and energy issues

 

Author:  Vincent P. Gutschick

            Professor of Biology, New Mexico State University, MSC 3AF, Las Cruces, NM 88003

            (My affiliation is for identification only; I do not purport to represent the views of the

                   regents of the university or other authorities)

            My qualifications to offer this analysis are detailed below, after the quick summary

 

This page is an ongoing exercise.  I will add more citations and links.

 

Jumping into biofuels – is it a good idea, and particularly for New Mexico?

 

Yes, some big money is going into biofuels (BP sets up $500M institute at the University of California, Berkeley; Los Alamos National Laboratory and partners go for a proposal up to $250M to the U. S. Dept. of Energy)

 

However, biofuels have a limited place in the energy economy

The simple message is that biofuels will require massive land conversion and water use, on a scale unprecedented in U.S. history, if they are to be a significant part of the solution of transportation fuels:

  • Biomass yields per land area are strictly limited by plant physiology and the diffuse nature of solar energy; expect less than 30 dry metric tonnes per hectare, or 12.5 tons per acre.
  • Energy yields are debited by energy inputs need to grow crops and to process them to fuel.
  • Consequently, huge land areas would be needed to provide even a fraction of fuel needs.  To supply all our transportation fuels would require 450,000 square miles, more arable land than we have have left.
  • Water use per unit of biomass is high, and is also fixed by plant physiology and the realities of climate.
  • Biofuels would need to be raised on land less suited to crops and more in need of irrigation.
  • The resultant water demands would exceed the total of all current irrigation and would far exceed any plausible sources of sustainable water yield.  We are already beyond sustainable water use without biofuels.
  • Net result: biofuels have only a modest place in the energy economy.  Rational planning for them, along with other alternatives, is needed.

   Other alternatives to fossil-fuel replacement include

  • Alternative energy sources – photovoltaics, solar thermal, wind power, etc.
  • Increases in efficiency of cars and trucks – plug-in hybrids, lighter vehicles
  • Incentives in tax and market structure to reduce commuting distances, etc.

 

    Do big commercial investments gainsay this analysis?  After all, $0.5B (billion) is a small fraction of our energy budget.  However, one should compare this to U. S. purchases of imported oil, alone, accounting for about $300B annually!  BP knows what they’re doing, with biofuels as a niche market, not the magic bullet for energy independence.

 

Are biofuels the sustainable and ethical way to go?

   They are renewable, and their production is sustainable, but only after a fashion:

     “After a fashion” because farming them currently uses considerable fossil fuel; the consequent reduction of fossil fuel use in producing a unit of vehicular fuel is modest.

     “After a fashion” also because cultivation of any soil increases erosion and generates pollution in rivers from fertilizer leaching (cf. the “Dead Zone” that this causes in the Gulf of Mexico). There are good and bad ways to minimize these effects, but the catchword is only “minimize.”

    Arable land is limited.  Is it ethical to convert cropland to biofuel farming in a world of food shortages?  While it is true that food shortages are as much an invention of food distribution systems as they are a fact of crop failure, it is inescapable that less cropland means greater food shortages.  Biofuels are certainly not going to solve the food distribution problem.

   Is it wise or even financially practical to raise biofuel crops in the West and in New Mexico in particular?  To be competitive economically at any significant rate of production (single-family farms notwithstanding), biofuel crops would have to be irrigated.  Irrigation water is severely limited  already in New Mexico, which is in a protracted legal battle over water allocation  with Texas and Mexico over water; drought cycles put us into shortfalls increasingly, and the Rio Grande runs dry episodically.

    Overall, the answer to the question of sustainability and ethicality is, No, not on large scales and certainly not in the dry West.

 

I offer that other sustainable energy resources are far superior, certainly on the large scales needed – photovoltaics provide an example.   Even better in every case that has been investigated, energy conservation pays back much better than increasing energy supplies at ever-increasing prices.   Let’s do it right and think about it with the optimal input from science, economics, and politics.

 

In the closer focus on New Mexico itself:

I would like to see New Mexico be a leader in the best technologies.  I cannot see biofuels as an answer.  This seems to run counter to what big investors say, such as BP (half-billion dollar deal with UC, Berkeley).  However, these investors know that biofuels are a niche, and, in the grand scheme, a small niche for a sustainable economy.  BP is still researching  photovoltaics – and manufacturing them on a big scale, and the R&D investments by Japan and Germany, among others, are striking.   I note also that these investors are carrying the ball on biofuels; we don’t need to be small players far back in the pack.

 

Other voices of caution on biofuels:  Citizens of Oregon have been warned about the high costs – both economic and environmental – of biofuels.

 

 

SOME DETAILS

Here is a very basic calculation of land and water needs, not to overlook need for fertilizer and other inputs. 

   Biomass yields per area are limited by plant physiology and the diffuse nature of sunlight

* The highest biomass growth rates, on an annual basis, approach 60 metric tonnes of dry biomass per hectare (about 25 tons per acre).  This rate is attainable only in areas with multiple crops per year (subtropics, which means, in the U.S., only Hawaii).  A more likely average with optimal management is perhaps 30 tonnes per hectare.  The harvestable fraction for fuels (harvest index) is somewhat less than half, certainly in corn.  This can rise to as much as 90% (say, 27 tonnes per hectare)  if cellulose in plants can be digested to sugars with new technology.

Raw energy value of biomass has to be discounted for energy to grow and process crops

* The energy value (enthalpy content) of dry biomass averages 19 kilojoules (kJ) per gram, or about 1800 large calories (ordinary food calories) per pound.  Thus, the gross energy from 27 tonnes (27 million grams) of dry biomass per hectare is about 513 GJ (gigajoules, or billion joules) on an annual basis.

* We have to debit this for (1) energy inputs in fertilizers and farm operations.  These have typically been significant, at least 1/3 of gross energy; David Pimentel at Cornell and others have detailed this.  Let’s go to 342 GJ annually; (2) energy costs of

- drying the biomass (for direct combustion in a power plant, useful for providing energy to electric vehicles).  You can do this for free with solar drying, but that requires more land, reducing yield per area by at least 1/3

   or

- distilling ethanol from fermentation (which loses another 1/3 or so of energy content)

   or

- chemically and thermally  transforming biomass to petroleum-like hydrocarbons (making biodiesel directly, e.g.)

Net result of these debits is that we’re down to an energy content of no more than 228 GJ per hectare, annually

* We may now convert this best yield to equivalent volume of gasoline or diesel.  The enthalpy content of either of the latter is about 40 kJ per gram; given about 2600 g in a gallon of fuel, this equates to about 104 MJ per gallon.

* Divide the final energy yield in biomass utilization by this last figure and we get that a hectare could yield around 2190 gallons of fuel.

Fuel use is huge, and, consequently, so is the crop area needed for biofuels

* U.S. consumption of transportation fuels is about 700 million gallons per day, or 256 billion gallons per year. 

* To supply that amount of fuel would require (256 billion)/2190 hectares, or about 117 million hectares of land.  This is about 288 million acres or 450,000 square miles.  This exceeds all the extra arable land in the U.S.

Water use to grow crops is high and cannot be improved much

* Water use to grow crops is set by inexorable limits on the water-use efficiency (WUE) of plants.  This is a topic on which I am an expert.  WUE is set by both the physiology of the plant and the local meteorological conditions.  One group of plants has a photosynthetic pathway called “C4” and has approximately twice the WUE of other plants.  The C4 plants include corn, sorghum, and a variety of warm-season grasses (in cold weather, a critical enzyme in C4 plants dissociates into two nonfunctional subunits).  I can detail the calculation of WUE, perhaps at another time.  Its value for C4 plants at mean continental temperatures and humidities is about 1 gram of biomass made per 300 grams of water transpired (lost to the air); WUE is higher on a short-term basis, but drops to this over the season, based on losses of biomass (sugars) for biochemical maintenance processes inside the plant.

 Improving the delivery of water, as with drip irrigation, pushes us closer to the minimal water use, but the minimal water use is inescapably large.  Drip irrigation has its own limitations, too; salt buildup in soil is changed, not eliminated (a whole topic in itself).

Water needs for biofuels to replace all current transportation fuels would be very high, beyond all available sources

* If we were to grow enough biomass for all transportation fuels at current usage levels, we would use nearly 80 trillion gallons of water annually, or 230 million acre-feet in U.S. units.

* Much of the water inputs could come from natural precipitation, but much would have to come from aquifers.  We irrigate about 8% of our crops now.  Much of the land for biofuels production would have to come from marginal land, not used for food crops.  This is largely in areas with insufficient rainfall, so that irrigation would have to increase to the equivalent of perhaps half the current farm area again, or about 6 times current aquifer use.  We are already depleting our existing aquifers with current use. 

* Exacerbation of soil erosion and habitat destruction are an additional issues that strongly constrain the use of agricultural land for biofuels.  I offer no details here; I generated a report on this some time ago, in 1981, for an international energy conference.  The issues have not changed since then.

 

Only a modest role for biofuels

     In summary, both land and water use would be insupportable in the extreme if we were to turn to biofuels for any major part of the transportation fuel supply – not to add in our other fossil fuel usage, which total 4 times our transportation usage.

     Biofuels at sustainable rates of land exploitation and water use can have a very, very modest impact on fuel supplies or on general energy supplies.  For a small list of uses, they may be worth developing. 

 

Other avenues to sustainable energy supplies and less dependence on fossil fuels

For our challenge in the large, of getting by with lower fossil fuel consumption (and CO2 generation), other avenues are much more worthwhile:

*  I have already cited alternative energy sources.  One such source is photovoltaic cells.  These could be used to provide energy in general or for electric vehicles specifically (the new Tesla car, to be produced in New Mexico, is a catchy example.  Plug-in hybrids are an even better energy-saver).  These, too, require large areas to be covered, because they are currently only 15% efficient as energy produced per unit solar energy intercepted….but 15% is a lot better than crops at less than 1%!...and photovoltaics don’t use water once they are manufactured.

* Energy efficiency is always the cheapest “source.”  This means not only fuel-efficiency standards but new transportation technologies (plug-in hybrids again; lighter vehicles) and new transportation strategies (not only mass transportation but reducing commute distances by combinations of tax and market restructuring for homes; too many people are compelled to live too far away from work for affordable housing).

 

 

My qualifications

 

    My CV is online at http://biology-web.nmsu.edu/vince/

   

    General qualifications in highly quantitative studies such as this issue demands:

        Ph. D. in chemistry (chemical physics) from Caltech, completed Aug. 1971 and

           issued June, 1972.  Follow-up postdoctoral and term faculty work at UC, Berkeley,

           Yale, and Los Alamos labs

Continuous research record, to date, in chemistry, physics, and biology using quantitative  methods (mathematical/computer modelling, esp.; extensive field and lab research, including breeding crops for water-use efficiency); career research award from NMSU, April, 2006; invited speaker at 5 international conferences; 1 patent for electronic sensors; published collaborations with researchers from 10 universities and 3 national laboratories in the U. S., Mexico, Australia, and France

Organizational and administrative experience in science issues: obtaining and administering a series of research grants; program officer at the National Science Foundation, administering a cluster budget of $25M; director of NSF-EPSCoR-funded Institute for Natural Resource Analysis and Management; co-leader of biosciences research cluster at NMSU, including planning for research institute

 

    Energy issues: I did considerable work earlier, directly on energy issues:

       Life-cycle energy costing of solar energy (thermal, photovoltaic)

       Environmental assessments of alternative energy sources (coal liquefaction, report, 1978;

           hot dry rock geothermal energy, report, 1978)

       Sustainability of fossil-fuel use in agriculture for fertilizer production (this really

          launched my career in that area)

Communication  on issues: participation in international conferences (nitrogen fixation,  Madison, WI, 1978; energy per se, Berlin, 1981); teaching courses in global change four times at New Mexico State University, as well as broader-focus courses in general biology, ecology, plant physiology, plant ecology, biophysical ecology, physiological ecology, biological modelling, and biological numeracy

 

   Expertise in plant physiology, ecology, and agriculture:

-  44 peer-reviewed journal articles and book chapters, 1 sole-authored book, and 6 reports on plant physiology, growth limits, and responses to the environment, including extreme events.  Including articles in chemistry, physics, and energy issues, I have a total of 52 journal articles, 11 reviewed book chapters and conference proceedings papers, 1 sole-authored book, 9 reports, and 1 technical film.

- 20 of the above articles and 5 of the reports directly address agriculture

-  4 more articles and 1 book chapter address remote sensing of plant performance

- Sabbaticals at CSIRO Plant Industry in Canberra, Australia,  LaTrobe University in Melbourne, Australia, the Carnegie Institution at Stanford, and the agronomic university (ENSA-M), Montpellier, France