05 December 2009

Scrap Irrigated Biofuel Crops & Plant Solar Farms!

After thinking some more about the numbers in yesterday's blog, here is a revolutionary idea: take irrigated biofuel crops already existing in the sunny Southwest (including California) out of production and put solar farms on those fields instead. Why? With no additional land used, we'ld have more energy in the grid, less chemicals in groundwater, less groundwater overdraft, and/or water leftover for the rest of us (including the rest of agriculture).

How is that going to work?

Let's start with some numbers on corn, currently the main source of ethanol fuel:

2009 California corn acreage: 550,000 acres
2009 Arizona corn acreage: 45,000 acres
2009 New Mexico corn acreage: 140,000 acres
2009 Utah corn acreage: 65,000 acres
2009 total Southwest corn acreage: ~ 800,000 acres
2009 Colorado corn acreage: 1,100,000 acres

2009 United States corn acreage: 86 million acres
2009 United States ethanol corn acreage: ~ 22 million acres (25% of total corn acreage)
2009 United States irrigated ethanol corn acreage: ~ 1-2 million acres (based on 2003 USDA statistic about the percentage of irrigated ethanol corn - I would guess it is actually higher now. In fact, a recent Argonne National Lab report, p. 3-27, estimated the irrigated fraction of biofuel acreage to be "less than 10%").

How much of the 800,000 acres of Southwest corn is used for ethanol - I am not sure, but it is probably not 25%. In California, much of the corn acreage is used to produce sileage for the California dairy industry (which produces more then one-fifth of the U.S. cheese and milk). Even if not a single acre of Southwest corn was used for ethanol and all of it went to sileage on Southwest dairies: I speculate that with the same subsidies that are currently used to ship Midwest corn to Western U.S. ethanol plants, we can ship corn from the Midwest to Southwest dairies to replace the needed sileage.

My point is: whatever corn acreage in the Southwest we convert to solar farms, we can replace the lost sileage for dairy production by taking some of the ethanol-destined corn from the Midwest and then using it for sileage in lieu of energy production. Looking at the numbers, we still end up with a net gain in energy - and a net gain in water!

Whether it is actual biofuel corn that is bulldozed over or whether it is sileage corn that the dairies replace with Midwest ethanol-corn-turned-dairy-sileage, let's assume that we can achieve a 1:1 replacement of 2009 ethanol-corn acreage with solar farm acreage. Using the water and land use intensity values mentioned in my last blog, here are a few basic energy systems scenarios and their water and land use benefits:

Scenario 1. Realize the total solar power currently planned for the Southwest - by converting corn fields to solar farms.

We would need to convert the sunniest 100,000 acres of the current irrigated corn acreage in the Southwest (approximately 13% of the current Southwest corn acreage) into solar farms to generate approximately 12,000 MW of energy. I wouldn't be surprised if those 100,000 acres aren't already used for growing irrigated biofuel corn in the Southwest! Another perspective: 100,000 acres would be 20% of the irrigated acreage in sunny Imperial Valley.

5 times more energy per converted acre (land use intensity is five times lower for solar than for biofuel)

700 times less water use: Of (approximately) 230,000 acre-feet of water evapotranspired on 100,000 acres of irrigated corn (see.e.g., our paper, Table 1 ), less than 2,500 acre-feet would be needed to dry-cool the solar-farms. The other 227,500 acre-feet of water would be available for other uses.... (assuming all solar farms are of the dry-cooled variety).

Scenario 2. Generate 100% of the electricity used in CA, AZ, NM, CO, and UT with solar farms, 450 million MWh (in 2007; US Total: 4,100 million MWh).

The installed solar power to generate this much energy would have to be on the order of 300,000 MW - six-hundred solar farms of 500 MW each - and 4,000 acres each. Together, these farms would need approximately 2.4 million acres of land. That is 120% of the combined corn acreage in the Southwest and Colorado. This acreage is also just about equal to the total U.S. acreage that is currently irrigated to produce ethanol (see above)!!

Over 10% of 2007 U.S. electricity demand generated from renewable solar on one-tenth of the land currently in use for ethanol production.

Assuming that 80% of that land comes out of currently irrigated corn production, with a consumptive use of ~2.3 acre-feet/acre, the amount of water savings is 4.5 million acre-feet - enough to meet more than one-third of the total urban and industrial water demand in these five states.

Furthermore, assuming an average energy use of 1 MWh to produce 1 acre-foot of groundwater or surface water (from a very enlighteningand  article by Dana Larson and others at the Bren School, UC Santa Barbara), an additional 4.5 million MWh of energy are saved every year.

Scenario 3. Replace the entire current U.S. acreage of ethanol-corn with solar farms.

Well, I am not sure about the efficiency of solar plants in much of the Midwest (where most ethanol-corn is grown), when compared to the Southwest, but at 10 times more land than in scenario 2, that ought to get us perhaps five times the amount of energy of scenario 2 or close to 50% of the total U.S. electricity use in 2007 - with the potential to replace all natural gas plants (22% of U.S. electricity) and half of all coal-powered plants (coal-powered plants produce half of the U.S. electricity). And we would save at least all the irrigation water of scenario 2 and then some.

But we would loose all the ethanol - can we use the natural gas saved in the process instead? Natural gas produces 900 million MWh of energy in the U.S (in 2007). On the other hand, 22 million acres of displaced ethanol-corn, at 178 bushels per acre, and with 17 bushels of corn to make 1 MWh, are worth 230 million MWh. We just gained four times the energy on the same land!

So no kidding: take out the ethanol corn (and perhaps not just the irrigated variety), and bring on the solar farm!

No doubt, these are hypothetical scenarios - there are a lot of other questions to ask and challenges to address (e.g., new crop distribution to take advantage of where the sun is, transportation systems adjustments, electricity transmission, carbon cycle impacts, economic impacts on farming regions, aesthetics of corn fields vs. solar panels) - but the big picture numbers cannot be argued away. Perhaps a key limitation is the ability of our national energy grid to deal with such large penetration of an intermittent energy source. With smart adjustments to our current grid, about 20% - 30% of our energy mix could come from an intermittent source such as solar (also see Denholm & Margolis' article in Energy Policy, 2007).

The most intriguing aspect of this comparison is that it is based on a replacement of one type of renewable energy-crop with another renewable energy "crop" - on the same currently used land - at five times the output, millions of acre-feet of (ground)water saved, and a lot of potential groundwater and surface water pollution from ethanol-corn production avoided (my main motivation to look at these scenarios). [Also check the numbers in this article].

Can we figure out the incentives needed to make this work in a free-market economy?

Addendum, 15 March 2010:

A very good friend of mine is working on environmental impact reviews for solar power plants in Arizona (how did all my friends get into solar so suddenly?).  She pointed out yet another technology in the array of concentrating solar power (CSP) technology: reflector dishes with Stirling engines, currently brought to market by Stirling Energy Systems. These systems use no water (perhaps for washing the mirrors?) and require little land preparation (according to my friend, the pole supporting the dish is simply and quickly rammed into the ground). Each dish has a 25kW engine and two proposed facilities (Solar One in Calico and Solar Two in Imperial Valley) would be 8,200 acres for 850 MW and 6,500 acres for 750 MW, respectively - approximately 10%-15% more landuse intensive than the 4,000 acres for 500 MW cited and used in my recent blog (which I used as the basis for the above computations).

Wow - what a concept! These SunCatchers(TM) seem (to a naiv academic at least) to be the perfect crop for business-savvy farmers to put into their overall crop rotation. Here is a proposal for a great water and solar farm:

The farmer leases the land to folks like Stirling Energy Systems (SES) that will install ("grow") SunCatcher(TM) dishes on the farm fields to replace the ethanol corn, while the farmer keeps watering the underlying barren land as part of an intentional water recharge project - without the farm chemicals (fertilizer, pesticides) and without the salinity increases in groundwater recharge from irrigated ethanol corn or other agricultural crops. The heavy equipment for land preparation and dish installation is already on the farm anyway, the infrastructure for the recharge project (in surface water service areas) is already in place, including water rights, delivery canals, and distribution system. And the apparently "simple" installation of the SunCatcher(TM) means that the farmer doesn't need to buy into this technology forever. The lease could be for a few years. SES could move the dishes to another site for the next lease period (so it does NOT have to look like this)

The question is only - can it be done to give the farmer something around a $500/acre net income, which is the average net farm income in CA - about 10 billion dollars on 20 million acres. According to "Agriculture Online" somewhere between $300 and $500/acre is also the net income generated for a typical corn farmer at 178 bushels/acre (see my recent blog) at 2009 corn prices of $4/bushel  - also confirmed by the USDA economic statistics on corn.

On the water market side, a California farmer could generate something on the order of one to a few hundred dollars per acre by recharging from one to five acre-feet of water into a groundwater bank, if (s)he sits in the right location for groundwater banking. Some farmers already do this by simply fallowing their land for so-called in lieu recharge arrangements.

On the solar energy side, a California farmer would need to be paid about $2 per MWh - above and beyond any cost for renting, installing, and maintaining the SunCatchers(TM) -  to generate $400 net income per acre annually (I am using the solar land use intensity of 5 acres/1,000 MWh that I presented in my recent blog). That is 0.2 cents per kWh for those of us household customers used to paying about 10 cents per kWh. In other words: to make this work for a farmer, Stirling Energy Systems and other companies need only pay a small fraction of the price that the generated energy is worth to pay the farmer some rent on her/his land. And if they increase the rent/lease offer (say 0.5 cents/kWh instead of 0.2 cents/kWh) - then (I assume) it would be a real incentive for the farmer to go solar, since (s)he is now looking at net earning of $1,000/acre.

....now I just need to find my 100 acre farm...(and cut a deal with SES). I'll let my friends chime in on the hurdles to pass the EIR. Perhaps I can claim SunCatchers(TM) to be just another crop - then, as a farmer, I would not have to implement a cumbersome EIR at all!!

Some of these solar power projects will be going in very fast under ARRA - this could become a model for installing solar power projects on current ethanol corn (or other agricultural) fields. A very interesting (but in total acreage limited) option is to build solar (CSP) facilities on already disturbed non-agricultural land that is not used otherwise (former mining sites, brownfields, etc.) - check out the "Restoration Design Energy Project" in Arizona. For a huge longer term project with a fast track pilot, check out LA Water & Power's Owen's Valley solar project.

Last, but not least, Derek Abbott just published a fine review of global energy alternatives - and the Stirling dishes are his favorite alternative.

Addendum, 9 January 2010:

A comparison of land coverage (square meter per GWh generated) for a number of different energy sources, including coal, wind, solar, and biofuels, was recently published by Vasilis Fthenakis and Hyung Chul Kim in "Renewable and Sustainable Energy Reviews". The article confirms the conclusion above.

Similarly, below is the abstract of a related article that compares energy-solutions based on environmental impacts. The article "Review of Solutions to global warming, air pollution, and energy security" is by M. Z. Jacobsen, Energy & Environmental Science 2(2):148-173, 2009.

This paper reviews and ranks major proposed energy-related solutions to global warming, air pollution mortality, and energy security while considering other impacts of the proposed solutions, such as on water supply, land use, wildlife, resource availability, thermal pollution, water chemical pollution, nuclear proliferation, and undernutrition. Nine electric power sources and two liquid fuel options are considered. The electricity sources include solar-photovoltaics (PV), concentrated solar power (CSP), wind, geothermal, hydroelectric, wave, tidal, nuclear, and coal with carbon capture and storage (CCS) technology. The liquid fuel options include corn-ethanol (E85) and cellulosic-E85. To place the electric and liquid fuel sources on an equal footing, we examine their comparative abilities to address the problems mentioned by powering new-technology vehicles, including battery-electric vehicles (BEVs), hydrogen fuel cell vehicles (HFCVs), and flex-fuel vehicles run on E85. Twelve combinations of energy source-vehicle type are considered. Upon ranking and weighting each combination with respect to each of 11 impact categories, four clear divisions of ranking, or tiers, emerge. Tier 1 (highest-ranked) includes wind-BEVs and wind-HFCVs. Tier 2 includes CSP-BEVs, geothermal-BEVs, PV-BEVs, tidal-BEVs, and wave-BEVs. Tier 3 includes hydro-BEVs, nuclear-BEVs, and CCS-BEVs. Tier 4 includes corn-and cellulosic-E85. Wind-BEVs ranked first in seven out of 11 categories, including the two most important, mortality and climate damage reduction. Although HFCVs are much less efficient than BEVs, wind-HFCVs are still very clean and were ranked second among all combinations. Tier 2 options provide significant benefits and are recommended. Tier 3 options are less desirable. However, hydroelectricity, which was ranked ahead of coal-CCS and nuclear with respect to climate and health, is an excellent load balancer, thus recommended. The Tier 4 combinations (cellulosic-and corn-E85) were ranked lowest overall and with respect to climate, air pollution, land use, wildlife damage, and chemical waste. Cellulosic-E85 ranked lower than corn-E85 overall, primarily due to its potentially larger land footprint based on new data and its higher upstream air pollution emissions than corn-E85. Whereas cellulosic-E85 may cause the greatest average human mortality, nuclear-BEVs cause the greatest upper-limit mortality risk due to the expansion of plutonium separation and uranium enrichment in nuclear energy facilities worldwide. Wind-BEVs and CSP-BEVs cause the least mortality. The footprint area of wind-BEVs is 2-6 orders of magnitude less than that of any other option. Because of their low footprint and pollution, wind-BEVs cause the least wildlife loss. The largest consumer of water is corn-E85. The smallest are wind-, tidal-, and wave-BEVs. The US could theoretically replace all 2007 onroad vehicles with BEVs powered by 73 000-144 000 5 MW wind turbines, less than the 300 000 airplanes the US produced during World War II, reducing US CO2 by 32.5-32.7% and nearly eliminating 15 000/yr vehicle-related air pollution deaths in 2020. In sum, use of wind, CSP, geothermal, tidal, PV, wave, and hydro to provide electricity for BEVs and HFCVs and, by extension, electricity for the residential, industrial, and commercial sectors, will result in the most benefit among the options considered. The combination of these technologies should be advanced as a solution to global warming, air pollution, and energy security.

Coal-CCS and nuclear offer less benefit thus represent an opportunity cost loss, and the biofuel options provide no certain benefit and the greatest negative impacts.


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