Study Suggests That Optimal Use of Bioenergy as Fuel or Electricity Depends on Market and Regulatory Policy Contexts; Higher-Level Assumptions Can Constrain Questions and Affect Results
30 September 2010
A new study by a team from UC Berkeley and Stanford University suggests that determining the optimal use of biomass to reduce greenhouse gas emissions—i.e, conversion to fuel molecules or to electrons—depends on market and regulatory contexts that are outside the scope of attributional life cycle assessments (LCA).
A 2009 life cycle analysis by Campbell et al. suggested that converting biomass into electricity for EVs abates more GHG emissions than does converting biomass into liquid fuels for use in today’s conventional vehicles. (Earlier post.) Using that as an example, the new study by Lemoine et al. notes that those results assume that bioelectricity generation displaces gasoline.
| Background: Two Styles of LCA |
|---|
| Two styles of LCA have emerged in the literature, the authors note: attributional and consequential. |
| Attributional LCA is a static analysis based on a product’s supply chain. Consequential LCA considers the net environmental effects induced by a change in production. |
| Both styles of LCA have been used in recent regulations aiming to reduce GHG emissions from the transportation sector. |
| Attributional LCA tempts analysts to draw conclusions that ignore the market conditions that affect ultimate environmental outcomes. Consequential LCA, the authors write, recognizes that environmental effects are not limited to a single supply chain’s impacts and generally depend on policy and market contexts; however, the results of consequential LCAs can also mislead if presented without useful framing and sensitivity assessments. |
Instead, they argue, under existing institutional and technical arrangements, bioelectricity production does not cause a reduction in gasoline use.
Electricity from all sources flows into the grid and is used to meet instantaneous system-wide demand. Bioelectricity could only displace gasoline if its generation were to increase charging by electrified vehicles already in the fleet or if its generation caused vehicle purchases to shift from gasoline-fueled vehicles to electrified vehicles.
Yet owners of existing electrified vehicles are unlikely to vary their charging habits according to the quantity of bioelectricity on the grid. Further, decisions to purchase electrified vehicles and decisions to use biomass as a primary fuel for electricity are made by different people, at different times, in different places, and without knowledge or concern for the others’ decisions.
Unless vehicle purchasers expect additional bioelectricity generation to substantially reduce electricity prices, it is difficult to imagine plausible technological or policy mechanisms that would link these decisions such that each increase in biomass electricity production is met with an equal expansion of electrified vehicle charging as well as a decline in gasoline vehicle fueling.
A more realistic assessment of GHG mitigation benefits would recognize that an increase in bioelectricity generation in fact recognize that an increase in bioelectricity generation in fact displaces other sources of electricity. The specific benefits depend on the type of electricity replaced, which in turn depends on the structure of the regional electricity market.
—Lemoine et al.
In other words, bioelectricity’s advantage over liquid biofuels depends on the GHG intensity of the electricity displaced. Bioelectricity that displaces coal-fired electricity could reduce GHG emissions, but bioelectricity that displaces wind electricity could increase GHG emissions.
Furthermore, they note, while a proper bioenergy life cycle assessment can inform questions about a bioenergy mandate optimal allocation between liquid fuels and electricity generation, questions about the optimal level of bioenergy use require analyses with differed assumptions about fixed (taken as given) and free (allowed to vary) parameters.
To address this, they developed a typology of modeled assumptions for bioenergy analyses that includes two dimensions of variability: whether the vehicle fleet is fixed or free, and whether the magnitude of overall bioenergy use is fixed or free.
The choice of fixed and free parameters determines whether a model can inform policy decisions about the design, the magnitude, or the appropriateness of a bioenergy mandate. How such a bioenergy mandate should weight bioelectricity versus biofuels depends on the GHG intensity of the electricity that would be displaced. How much biomass should be used for energy depends on the other options for decarbonizing liquid fuels and electricity supply and on the broader social costs of producing energy crops and altering land use patterns.
Finally, whether a climate policy portfolio should include policies specifically aimed at promoting bioenergy and/or electrified vehicles depends on the costs, benefits, and feasibility of such policies relative to other abatement options. The chosen combination of fixed and free parameters not only affects the model’s results but also constrains the set of policy questions to which the results apply.
—Lemoine et al.
Their paper is in press in the ACS journal Environmental Science & Technology.
Resources
Lemoine, D.M., R.J. Plevin, A.S. Cohn, A.D. Jones, A.R. Brandt, S.E. Vergara, and D.M. Kammen (2010) The climate impacts of bioenergy systems depend on market and regulatory policy contexts. In press. Environmental Science & Technology doi: 10.1021/es100418p
Their logic is flawed here because they have the wrong baseline assumption: Farm land IS being used to grow corn, or other crops for fuel today.
Sure, it would be cleaner to use wind, solar or hydro rather than growing crops and either burning them for electricity or converting to liquid fuels and then burning it in an engine. DUH.
So there argument really comes down to this: Should we be using land to grow biomass for energy?
HOWEVER, unless you can change congress and get them to stop subsidizing the growth of crops for fuel and stop farmers and big agribusiness...it WILL continue to be grown.
So, considering it WILL be grown for energy in our current political/economic environment, which is the more efficient way to use it? Electricity or conversion to liquid fuels???
Posted by: DaveD | 30 September 2010 at 07:57 AM
I think you missed the point of the article. Given X amount of biomass, the "optimal" use depends on the policy choices and the regulatory framework. The individual choices between ICEV and BEV are largely decoupled (though factors like oil-price spikes will probably drive consumer demand for BEVs).
One of the factors not mentioned ITA is carbon levies. At some price for carbon emissions, the cheapest electricity comes from nuclear, hydro, wind and biomass. Conversion of biomass to liquids entails losses, so the biomass-electric system delivers more carbon reductions and tax savings.
Posted by: Engineer-Poet | 30 September 2010 at 09:02 AM
"So there argument really comes down to this: Should we be using land to grow biomass for energy?"
The quick answer is yes. Since we grow 78% of our corn crop for animal feed why complain about converting a portion to domestic alcohol? Let the cows eat grass again. It is cheaper politically and financially than imported OPEC oil/gas at $8-10/ gallon REAL cost.
There is FAR more political will to end our addiction to foreign oil than to coddle GHG fears. Replacing foreign oil with domestically produced biofuels creates jobs, enhances security, stimulates local economies and is one more step toward energy independence.
Any who think GHG fears hold a candle to these political exigencies - are deluding themselves.
Posted by: Reel$$ | 30 September 2010 at 09:07 AM
If you have 100 million cars running methanol versus 1 million EVs, then the decision is clear. Corn stalks and cobs can make methanol. Switch grass and forest waste can create methanol.
Posted by: SJC | 30 September 2010 at 09:56 AM
Since we grow 78% of our corn crop for animal feed why complain about converting a portion to domestic alcohol? Let the cows eat grass again.
Where are they going to find this grass? It also needs land to grow on. What's the difference[energy wise] between
1) growing corn in a field and bringing it to the cows you're keeping in a pen and
2) growing grass in that field and sending the cows out to eat?
Posted by: ai_vin | 30 September 2010 at 10:07 AM
Switch grass can be grown on marginal land unsuited for just about anything else. 10 tons per acre and 100 gallons per ton yields 1000 gallons per acre times 100 million marginal acres. 100 billion gallons of biofuel would go a long way to reducing imported oil.
Posted by: SJC | 30 September 2010 at 10:25 AM
Engineer-Poet,
Well...kinda. I do get their point, I just think it is secondary to the fact that we are going to produce biomass regardless so it would be smart to make the most efficient use of the resulting energy.
I'm just a practical, get to the bottom line kind of guy. Clearly you don't use it to displace wind energy or solar. So ship it somewhere that they use the dirtiest coal and replace that in the grid (assuming you're going to use it to make electricity of course).
Posted by: DaveD | 30 September 2010 at 10:52 AM
Reel$$,
I COMPLETELY, 100% agree with you that it is so much easier to sell energy security in this environment than GHG. We waste our time and energy trying to sell GHG reduction to the non-believers and they fight us on everything. If we fight for energy security, American jobs and to stop sending over $400Billion a year out of our economy to buy foreign oil...that is a fight we can win.
And SJC is right about the fuel vs. electricity today. This won't be true in the long run because it is more efficient to make the electricity. You get a lot more miles of driving per acre from the electricity...once there are enough EVs to use it.
Today, we have 250million ICEVs and they can burn the ethanol now. They could burn methanol or butanol as well. In fact, we should have all cars be FF enabled so that we had that choice.
To me, the most important thing is to focus on reducing petroleum usage and the GHG reductions are a great side effect.
Posted by: DaveD | 30 September 2010 at 11:11 AM
When we get 100 million EVs they will use energy more efficiently. 2020,2030,2040, when will that be, lots of guesses. All new cars sold being FFV could get us to 100 million in 10 years. During that 10 years we build fuel plants. Making methanol from natural gas has the benefit that it can be made locally for any community.
Posted by: SJC | 30 September 2010 at 11:27 AM
Yeah, I'm an EV nut but there is no way we'll see 100 million of them anytime soon. We probably only have about 10,000 of them today, almost all home conversions plus a few Teslas.
With Nissan building production for 200,000 a year in Smyrna starting in 2012-2013, we'll be lucky to hit half a million to a million total by 2015. Maybe 3-5 million total by 2020 if things go really well.
I think Ford and GM have already produced about 10 million flex fuel vehicles and are ramping that number up every year. We could easily be to 50-100 million of those by 2020.
Posted by: DaveD | 30 September 2010 at 12:32 PM
GM has said they could make 1/2 of their cars FFV in just a few years. They make them in Brazil, so this is nothing new. If you make them run methanol, they run ethanol. Since it costs so little to make them FFV, it is a no brainer. This is an easy, affordable and effective solution to imported oil NOW, not 20 years from now.
Any city that has a natural gas main and maybe 100,000 people could have their own methanol plant locally. The trucks would only drive a few miles to the fueling stations. Less congestion and danger on the highways and a steady supply of locally sourced fuel. Now the tanker comes in to port, the oil goes to the refinery and the gasoline comes down the highway 50-100 miles. It is the way we have done it, but it is not the only way.
Posted by: SJC | 30 September 2010 at 12:47 PM
SJC finally says where he expects the methanol to come from: natural gas. Now, how much NG are you talking about, and where do you expect to get that?
If you're starting with NG, what's the pipeline-to-wheel efficiency vs. CNG?
Methanol has very different combustion characteristics compared to gasoline. It's said that engines optimized for gasoline can't get the best out of ethanol, and methanol would probably be the same only more so.
Posted by: Engineer-Poet | 30 September 2010 at 03:13 PM
I have long said that methanol would come from natural gas just like it does now. Over time, biomass could be used to make methane or methanol.
I have no idea why you want to pick a fight, that is juvenile. Just stick to the facts and advocate a position, this is not a school playground.
Posted by: SJC | 30 September 2010 at 04:08 PM
I'm raising the issue of the source because we've got problems brewing.
- Conventional NG is declining.
- Hydro-fraccing of shales may be causing severe water pollution, so the supply may shrink suddenly as new standards go into effect.
- Rumor is that the business is not cash-flow positive at current prices, so lots of players are going to exit the business and/or prices are going to shoot up.
- Biomass supply isn't equal to the task, either by the ethanol or methane route.
I'm not picking a fight. I'm hashing out the issues. Remember when ethanol from corn was the OPEC-killer? It turns out the whole US corn crop couldn't replace our imported oil. If we're going to bet on methanol, we should only bet as much as the likely payoff.Posted by: Engineer-Poet | 30 September 2010 at 08:21 PM
Natural gas estimates for the U.S. are 124TCuFt from coal bed methane alone. Total estimates for technically recoverable NG are 2586.9TCuFt. Canada has even more.
@ai-vin,
Sure you have to grow grass IF is replaces the corn feed diverted to ethanol. How about raising the price of feed and cutting consumption of Big Macs? There is also the proposition to grow algae to replace cattle feed - it's like grass and probably healthier for the cows.
Point is this is not an engineering issue - it is a political issue. We need domestic energy that provides jobs, security and economic benefits. EROI takes a back seat to these political pressures.
Posted by: Reel$$ | 01 October 2010 at 10:24 AM
124 TCF is less than 130 quads. The USA uses about 40 quads of petroleum per year. Also, "technically recoverable" does mean recovery is economical, or that it can be done by any means which meet environmental standards.
Posted by: Engineer-Poet | 01 October 2010 at 11:31 PM
Is going from one unsustainable fossil energy source (oil) to another (NG) worthwhile? Producing more NG from local Coal and Shales may sound good but could have serious side effects. Over 80% are against massive Shale Gas extraction in our area.
We may not have the liberty to choose. Our children and certainly our grand children will have to develop and use cleaner more sustainable energy sources. Nuclear, solar, wind, geothermal, Hydro etc are all mature technologies and could produce all the energy required for centuries.
Transition will generate a lot of talks and objections but it will happen. It is in our nature to do so.
Posted by: HarveyD | 02 October 2010 at 08:23 AM
We can gasify corn and sorghum stalks to make methane and methanol. We get about one two billionth of the energy the sun puts out but a few hours of that captured could supply the world's energy for a whole year.
Plants may not be efficient solar converters, but they cover a large area and we grow them for feed and food. If we can replace even half of the personal vehicle fuel with methanol made from plant cellulose, we can reduce oil imports from the middle east and OPEC.
All we need is the cars that run methanol/ethanol and we can have 100 million of those in 10 years at very little cost. Once that many cars are on the road, an alternate fuels industry can grow which will employ more people than the oil industry in the U.S. This is something we must do as soon as possible.
Posted by: SJC | 02 October 2010 at 11:31 AM
I'd say we need a greater push for EV's so that biomass can be used most efficiently. Why put time and money into methanol/ethanol refining when EV's make better use of the unrefined product? The whole liquid fuel/ICE paradigm is outdated and needs to be replaced.
Posted by: JRP3 | 02 October 2010 at 03:10 PM
We might have 1 million EVs in 10 years but we could have 100 million FFVs in 10 years. THAT is why you use methanol, you don't refine it you synthesize it cheaply and abundantly.
Posted by: SJC | 02 October 2010 at 03:17 PM
How cheap is methanol going to be if e.g. NG goes back to $8/mmBTU? What's the service life of an NG-to-methanol plant, and how long is the FFV stage expected to last?
Posted by: Engineer-Poet | 02 October 2010 at 09:17 PM
Why don't you do some research to find out and let us know.
Posted by: SJC | 03 October 2010 at 12:47 PM
Because making the case for your idea is your job.
Posted by: Engineer-Poet | 04 October 2010 at 06:12 AM
It is not my job, I think it is a good idea, I do not have to prove it to you.
Posted by: SJC | 04 October 2010 at 02:50 PM
If you want anyone else to think it's a good idea, you have to be convincing. Unsupported assertions don't count for much.
FWIW, I've done searches on the production cost of MeOH for much the same reasons as you. The cost is quite reasonable... as long as you have cheap hydrogen and CO or CO2 for free. That's the problem.
Posted by: Engineer-Poet | 04 October 2010 at 09:12 PM