The Globe and Mail ran a series on Saturday regarding the Baby Boomers now that their leading edge is on the cusp of retirement. The section includes a variety of issues, such as health, snarky commentary (my favourite type), and a documentary on tupperware. The timeline for the Boomer generation, Gen-X (the Bust), and Generation Why? (Baby Boom Echo) is given here. I am firmly ensconced in Generation Why?
Trying to make sweeping generalizations about the nature of a generation is somewhat useless, but we can look at the defining events of the baby boomer generation. First is the Cuban Missile Crisis. One can imagine what sort of impact this sort of trauma would have on young lives. The "Duck and Cover" ads (read: propaganda films) of the time were downright sinister. This has got to be the most widespread childhood trauma of the baby boomers. It wouldn't matter where you lived, or how rich your parents were, the fear of the bomb was over your head
In America the next major event would be the Vietnam war. However, Vietnam is not applicable to Western Europe or Canada. Furthermore, given the way people have reacted to 9/11 and the invasion of Iraq I think I can safely say that the Cuban Missile Crisis trumps Vietnam for psychological impact.
The relevance of Neil Armstrong and Buzz Aldrin landing on the moon is tough for me to analyze. I see it as posturing that accomplished nothing of significance, but I understand that it's one of the events that led to the general optimism of the baby boomer generation.
The next events that we would think would have a major impact on the collective consciousness of a generation would be the oil shocks of the early and late 1970s. Baby boomers were young adults at the time. While the oil shocks would have sweeping changes on the economy, the effect on psychology appears to be dependant on which continent you live on. In Europe and Japan attitudes changed; in North America the same generation later popularized the SUV.
In the 1980s and 1990s are mostly notable for what didn't happen. While Gorbachov and Sakharov did manage to bring down the Soviet Union, that only added to the general euphoria of the baby boomers. The 1990s were truly dull from my recollection. What didn't happen was any change to the unsustainable status quo. I think the overriding legacy from the baby boomers that we can quantify is the massive debts they're leaving behind as they retire. I'm not simply talking of publicly held debt, but pension and health entitlements, infrastructure investment, and the burgeoning energy and environmental crisis. They will probably be held up in history as the least sustainable generation.
The service payments on public debt consumes a major chunk of the budget of developed nations. This is a good life lesson against living off your credit card, although too many people seem to not have grasped this constatation.
On entitlements, in Canada the national pension plan has $100 billion in assets, as opposed to a box of IOUs in the USA. Our health situation is no better, however. As baby boomers age, one can easily invision massive pressure building on the health care system. Will we yun`uns be able to handle the demand baby boomers create for health care? The more pertinant question may be are we willing to pay for it? I would not be surprised to see the boomers force the issue of health care to the forefront due to their power as a voting block. However, I would also expect an eventual backlash.
Infrastructure debt seems to have maxed out in the mid-1990s. From what I've seen, that trend is slowly reversing itself. However, I would certainly take umbridge with the allocation of new capital for infrastructure. Mass transit has not even remotely kept pace with suburban development while the university system seems to have been overdeveloped compared to trades. The rise of MBA programs are a pox upon our lands while the electricity grid is in frighteningly bad condition.
The depletion of energy resources and the associated problem of climate change that comes with the burning of fossil fuels is the biggest issue, at least from my perspective. One thing I kind of miss with the Blogger software is the ability to run polls. It would be nice to survey people and see how the taxonomy of peak oilers fits with the various generations. (And yes, I am wondering if Doomers are predominately Generation-Xers.)
In the new millennium, there was the tragic day of 9/11 followed by the biggest non-sequitur ever, the invasion of Iraq. I do wonder how much of the reaction to 9/11 can be ascribed to a desire to counter the helplessness of baby boomers during the Cuban Missile Crisis. They've pretty much gone round a full circle and now we're right back at Vietnam.
25 June 2006
23 June 2006
Birthday
So Entropy Production was one year old as of yesterday. Such an anniversary presents a good opportunity to reflect on the general state of the blog, where it's been and the overriding themes:
- Electricity is my favourite energy carrier with high density chemical fuels as the second choice. Overall the economy and environment would benefit from a push to offset our petrochemical consumption with electricity − in particular the transportation sector.
- Intermittency of electricity sources such as solar and wind power is not a serious problem at present but it is likely to grow into one. I put a lot of emphasis on this issue. There is a need for some form of energy storage or flexible demand (such as electric vehicle charging). Solar power correlates reasonably well with peak demand while wind is a volatile electricity source. Some form of base-load power production is highly desirable.
- Conservation is necessary but proceeding at a fairly limited pace. Government action could raise the standards for many applications to increase their efficiency.
16 June 2006
Response to Comment of my Review
Oh, we're talking about biodiesel if is wasn't immediatly clear from the title on the post. I posted a review of a major National Renewable Energy Laboratory (NREL) study on soy-derived biodiesel. J.C. Winnie of After Gutenberg later published an extended comment on my review on his own blog that I would like to respond to.
The first statement I take umbrage with appears to be confusion over one problem with the energy return on energy invested accounting used within the NREL study:
I also said that the coproduct accounting stank because the meal is worth less (on a mass basis) than the oil, whereas NREL's accounting gave equal value to not just the meal but also the water content and hulls of the beans. Winnie casts some doubt on this assertion:
The last comment I would like to make regards the closing discussion:
With regards to Tad Patzek (and by extension David Pimental) they both like to include energy amortization charges for all the capital infrastructure used for the production of biofuels. The NREL study does not deal with this issue. It is a topic that will have to be saved for another time.
The first statement I take umbrage with appears to be confusion over one problem with the energy return on energy invested accounting used within the NREL study:
The authors failed to take into account any power input other than fossil fuel, i.e., they omitted electricity, which is a predominant energy input.This isn't what I said. I stated that "for the purposes of this study, this means the hydroelectric and nuclear power share," (of electricity). The study used a bouquet of energy sources intended to be representative of the USA as a whole. In the States, the share of nuclear and hydroelectric power (20 + 3 %) is not very big, so they are not omitting all of the electricity consumption from their energy balance equations, just a chunk of it. In a nation such as France, Canada, or the nordic and baltic states this would have had a much bigger impact.
I also said that the coproduct accounting stank because the meal is worth less (on a mass basis) than the oil, whereas NREL's accounting gave equal value to not just the meal but also the water content and hulls of the beans. Winnie casts some doubt on this assertion:
In another post, a Missouri farmer indicated that the meal when used as a high-protein animal feed is worth more than the biodiesel at current prices. Yet it may well depend upon where one looks and who does the looking. Reportedly, Biodiesel production in Indiana is rapidly increasing because the price of soybeans have become relatively cheap compared when compared with markets in other grain-producing regions in the Midwest, plus the demand for fuel in Eastern states is increasing.There is no need to rely on anecdotal evidence in this case. Entering the terms "wholesale price soy meal" into Google yields precisely the data we desire from the University of Cornell. If we open up Table 9(2).xls we'll find that a bushel of soybeans yields an average of 11.33 lbs. of oil and 44.26 lbs. of meal for the year 2004/5. We can calculate from the table that soy oil has a value of $0.2321/lbs. while meal has a price of $0.0915/lbs. Sometimes I want to leave something as an exercise to the reader.
The last comment I would like to make regards the closing discussion:
Speaking of accounting, such a narrow perspective omits acknowledgment 1) that, whether in Europe or North America, biomass-based power generation is likely to remain more cost effective than biofuel production, or that, as Tad Patzek continues to remind us, bottom line, “There simply isn’t enough arable land available in the world to grow the crops that would be needed to fuel our oil habit.”This is a bit of a non-sequitur, in that my original post didn't really attempt to address those issues. Entropy Production is a blog; an evolving narrative. I can't write a book chapter every post, so no one post will be a self-contained document. I only consider biomass energy solutions useful if they produce a portable, calorific, liquid fuel. Generation is just not on my agenda; there are too many better ways to generate electricity without invoking issues like soil erosion.
With regards to Tad Patzek (and by extension David Pimental) they both like to include energy amortization charges for all the capital infrastructure used for the production of biofuels. The NREL study does not deal with this issue. It is a topic that will have to be saved for another time.
14 June 2006
Ergosphere Implodes
Of all the things that could cause the Ergosphere to collapse into its attendant black hole I didn't think an unclosed 〈hr \ was capable of such a feat.
On a more serious front, I saw an interesting example of efficiency improvements driven by higher energy prices the other day. We were seeing a demo for a fumehood. For those of you who aren't familiar with such a piece of research apparatus, they essentially allow you to conduct chemistry experiments that might emit noxious fumes. The fumehood is a box within which a high airflow is passed. This laminar air flow prevents any gas from escaping into the laboratory environment.
Of course, the cost of conditioning all this air that passes through a fumehood is quite high. The engineer from the fumehood manufacturer say that the annual cost of heating and cooling air for a fumehood was $5.50 per cubic feet per minute flow rate. Our fumehoods cost approximately $10000 and have a constant flow rate of 620 cfpm. Hence the operating (energy) costs of the fumehood ($3410/annum) exceeds the capital investment in under three years.
In order to improve the energy efficiency of the fumehood the company has developed a variable flow system that reduces the flow rate when all the windows on the fumehood to the lab are closed. This is futher improved by adding an infrared motion sensor − similar to the type on automatic doors − that opens and closes the window (sash) when someone actually approaches the fumehood.
I just thought that this was an interesting anecdote of how industrial operations can improve their energy efficiency through high energy prices. Judiciously applied carbon taxes and efficiency subsidies could help further improve a huge number of industrial energy consumers. I know that my energy consumption at work (which would be categorized as industrial sectors) dwarfs my personal energy consumption.
On a more serious front, I saw an interesting example of efficiency improvements driven by higher energy prices the other day. We were seeing a demo for a fumehood. For those of you who aren't familiar with such a piece of research apparatus, they essentially allow you to conduct chemistry experiments that might emit noxious fumes. The fumehood is a box within which a high airflow is passed. This laminar air flow prevents any gas from escaping into the laboratory environment.
Of course, the cost of conditioning all this air that passes through a fumehood is quite high. The engineer from the fumehood manufacturer say that the annual cost of heating and cooling air for a fumehood was $5.50 per cubic feet per minute flow rate. Our fumehoods cost approximately $10000 and have a constant flow rate of 620 cfpm. Hence the operating (energy) costs of the fumehood ($3410/annum) exceeds the capital investment in under three years.
In order to improve the energy efficiency of the fumehood the company has developed a variable flow system that reduces the flow rate when all the windows on the fumehood to the lab are closed. This is futher improved by adding an infrared motion sensor − similar to the type on automatic doors − that opens and closes the window (sash) when someone actually approaches the fumehood.
I just thought that this was an interesting anecdote of how industrial operations can improve their energy efficiency through high energy prices. Judiciously applied carbon taxes and efficiency subsidies could help further improve a huge number of industrial energy consumers. I know that my energy consumption at work (which would be categorized as industrial sectors) dwarfs my personal energy consumption.
12 June 2006
Economy of a Solar-Electric Power Plant
I co-posted this over at theWatt.com.
Portugal is breaking ground on the worlds single largest photovoltaic (solar cell) electricity power plant. The plant, situated in Serpa, will cost €58 million to construct. It will have a peak power rating of 11 megawatts spread out over 60 hectares.
Portugal gets quite a lot of sun − not as much as Murcia or Sicily, but still a lot. According to RETScreen's database Evora (the closest inland location to Serpa in the database) gets 2.82 MWh/m2 per annum with the use of a two-axis tracking system. I did a quick calculation with RETScreen and came up with a 25.8 % capacity factor. That correlates to a annual power production of 25000 MWh. If amortized over 25 years, the facility will produce power for a rate of €0.093/kWh plus maintenance costs.
Paying 10 cents a kWh for a clean source of power seems like a good deal to me, and this is with global prices for photovoltaic modules drifting up to $5.50 / Wp.
Portugal is breaking ground on the worlds single largest photovoltaic (solar cell) electricity power plant. The plant, situated in Serpa, will cost €58 million to construct. It will have a peak power rating of 11 megawatts spread out over 60 hectares.
Portugal gets quite a lot of sun − not as much as Murcia or Sicily, but still a lot. According to RETScreen's database Evora (the closest inland location to Serpa in the database) gets 2.82 MWh/m2 per annum with the use of a two-axis tracking system. I did a quick calculation with RETScreen and came up with a 25.8 % capacity factor. That correlates to a annual power production of 25000 MWh. If amortized over 25 years, the facility will produce power for a rate of €0.093/kWh plus maintenance costs.
Paying 10 cents a kWh for a clean source of power seems like a good deal to me, and this is with global prices for photovoltaic modules drifting up to $5.50 / Wp.
11 June 2006
Thermal Storage, an Efficient Allocation of Resources?
Does the Lovins/passivehaus building construction theme render the concept of thermal storage systems for regulating the intermittency of renewable energy sources obsolete? In order to examine this question we would need to first compare the capital investment of each system. However, since neither is deployed in an quantity, this isn't really possible. The issue that can be analyzed then is the ancillary value of thermal storage to a renewable electricity grid versus the efficiency gains of the passivehaus concept.
Passive Home Concept
For those of you who have never come across the Amory Lovins schtik or the German Passivehaus building standards, it has been shown that residential or commercial structures can be built with practically no heating requirements. This is done through construction that is properly insulated and sealed with minimal air exchange and uses passive heating (or cooling, depending on climate) strategies. The passivehaus benefits from entropy in terms of home heating. Every electronic device is essentially a resistance heater in addition to its functional purpose, and every person an 80-100 W thermal source.
Scale of Thermal Storage
The most likely medium for thermal storage is water due to its low cost, heat capacity, and the fact that it is liquid and hence is easy to transfer heat with it.
The specific heat capacity of water is 4.184 KJ kg-1 K-1. The heat of fusion − the energy required to change the phase of water from solid ice to liquid water − is 334 KJ kg-1 or the equivalent of almost 80 K. Relative to 20 °C, ice stores a greater amount of cooling power than boiling water.
Consider data on space heating and air conditioning for the USA in 2001. I'll use the worst case: Northeast homes for heating and Southwest for cooling. I am going to ignore hot water heating even though it's significant because it's not relevant to the argument in the end. The average Northeast home uses 63 mmbtu/year for space heating. This works out to an average of about 0.18 GJ/day or 0.365 GJ/day during the peak heating season assuming some sinusoidal distribution. This is the equivalent of 87,000 kg K/day of water; if we store the water at 80 °C to heat the home at 20 °C then we need approximately 1.5 tonnes of water, or 1.5 cubic meters worth (nearly 400 gallons).
On the cooling front, the average Southwest annual electricity consumption is 4,000 kWh/year. If we use an average coefficient of performance of 3.o then the actual cooling supplied is 0.12 GJ/day or a estimated peak of 0.235 GJ/day. If, again, we assume the house is kept at 20 °C then 2/3 of a tonne of ice is required. Consider that 1-2.5 tons (of ice) are common ratings for a centralized air conditioning systems.
Taken over North America (say 100 million homes), these seem like significant numbers. 44 mmbtu of natural gas at $10/mmbtu is $44 billion dollars a year and the production of ~67 Megatonnes of CO2 . 2,300 kWh of electricity for cooling is a total of $18.4 billion dollars (at $0.08/kWh) per year and assuming coal power (at 900 g/kWh), 207 Megatonnes of CO2.
The North American GDP is about $12 trillion per year, so residential heating and cooling alone constitute 0.5 % of that. Scale-wise, there is plenty of potential for passivehaus or thermal storage systems. But can they be friends?
Heat Pump Efficiency
The coefficient of performance is how much heat is moved for a given amount of work (electricity in this case). Commercially air conditioners in the USA are rated based on a Energy Efficiency Rating (EER) which is the square of the COP between 80 F and 95 F (or about 300 K and 308 K). There is also a Seasonal EER (SEER) which is a different (more relaxed) standard. The theoretical COP for this temperature range is 37, but in reality most systems are in the range of around 3.5. The ultimate theoretical coefficient of performance of a heat pump is given by:
COP = TH / (TH - TC) = TH / ΔT
Herein lies a problem. As the temperature difference a heat pump has to cross increases its efficiency decreases. Normally an air conditioner only has to work across 8 K or so. However, if we want to use it to make ice, from a night-time temperature of 24 °C, then the ultimate efficiency of the system will only be a third normal. For a real-world system the drop in efficiency on a percentage basis will not be so precipitous but it will still be disadvantaged trying to make ice.
Overall it's a tough sell for thermal storage as a means of handling renewables intermittency. As we've seen, thermal storage sets efficiency against grid regulation. Generally, when we have schemes with competing criteria they fail to be economically attractive. Witness my investigation into solar thermal cooling. In that case there was a competition between the efficiency of the solar thermal collector and absorption chiller on the basis of temperature. Here we have competition on pure power. Yes, we can store off-peak power, but the effective round-trip efficiency is going to be unimpressive simply due to the drop of in performance of the heat pump.
There is still the possibility to run numerous appliances on a deferrable basis. Heat, air-conditioning and refrigeration all only need to maintain a given (if narrow) temperature range so with good insulation they should be able to run on relatively short duty cycles. Other appliances, such as the dishwasher or combination washer/dryer can be scheduled.
Chicken or Egg?
One problem with pumping efficient homes is that houses last for such a long time. One often heard meme in the peak oil world is that car fleets take too long to be replaced. Houses can be renovated, cars can't. Still if you are one of those people who think suburbia is evil (as opposed to just soulless) then the choice of whether to concentrate on improving the efficiency of houses or cars presents quite a quandary. From my point of view, I'm more concerned overall with climate change and more localized pollution of the air and water. If people want to live in rows of identical pink stucco houses... enjoy.
Passive Home Concept
For those of you who have never come across the Amory Lovins schtik or the German Passivehaus building standards, it has been shown that residential or commercial structures can be built with practically no heating requirements. This is done through construction that is properly insulated and sealed with minimal air exchange and uses passive heating (or cooling, depending on climate) strategies. The passivehaus benefits from entropy in terms of home heating. Every electronic device is essentially a resistance heater in addition to its functional purpose, and every person an 80-100 W thermal source.
Scale of Thermal Storage
The most likely medium for thermal storage is water due to its low cost, heat capacity, and the fact that it is liquid and hence is easy to transfer heat with it.
The specific heat capacity of water is 4.184 KJ kg-1 K-1. The heat of fusion − the energy required to change the phase of water from solid ice to liquid water − is 334 KJ kg-1 or the equivalent of almost 80 K. Relative to 20 °C, ice stores a greater amount of cooling power than boiling water.
Consider data on space heating and air conditioning for the USA in 2001. I'll use the worst case: Northeast homes for heating and Southwest for cooling. I am going to ignore hot water heating even though it's significant because it's not relevant to the argument in the end. The average Northeast home uses 63 mmbtu/year for space heating. This works out to an average of about 0.18 GJ/day or 0.365 GJ/day during the peak heating season assuming some sinusoidal distribution. This is the equivalent of 87,000 kg K/day of water; if we store the water at 80 °C to heat the home at 20 °C then we need approximately 1.5 tonnes of water, or 1.5 cubic meters worth (nearly 400 gallons).
On the cooling front, the average Southwest annual electricity consumption is 4,000 kWh/year. If we use an average coefficient of performance of 3.o then the actual cooling supplied is 0.12 GJ/day or a estimated peak of 0.235 GJ/day. If, again, we assume the house is kept at 20 °C then 2/3 of a tonne of ice is required. Consider that 1-2.5 tons (of ice) are common ratings for a centralized air conditioning systems.
Taken over North America (say 100 million homes), these seem like significant numbers. 44 mmbtu of natural gas at $10/mmbtu is $44 billion dollars a year and the production of ~67 Megatonnes of CO2 . 2,300 kWh of electricity for cooling is a total of $18.4 billion dollars (at $0.08/kWh) per year and assuming coal power (at 900 g/kWh), 207 Megatonnes of CO2.
The North American GDP is about $12 trillion per year, so residential heating and cooling alone constitute 0.5 % of that. Scale-wise, there is plenty of potential for passivehaus or thermal storage systems. But can they be friends?
Heat Pump Efficiency
The coefficient of performance is how much heat is moved for a given amount of work (electricity in this case). Commercially air conditioners in the USA are rated based on a Energy Efficiency Rating (EER) which is the square of the COP between 80 F and 95 F (or about 300 K and 308 K). There is also a Seasonal EER (SEER) which is a different (more relaxed) standard. The theoretical COP for this temperature range is 37, but in reality most systems are in the range of around 3.5. The ultimate theoretical coefficient of performance of a heat pump is given by:
COP = TH / (TH - TC) = TH / ΔT
Herein lies a problem. As the temperature difference a heat pump has to cross increases its efficiency decreases. Normally an air conditioner only has to work across 8 K or so. However, if we want to use it to make ice, from a night-time temperature of 24 °C, then the ultimate efficiency of the system will only be a third normal. For a real-world system the drop in efficiency on a percentage basis will not be so precipitous but it will still be disadvantaged trying to make ice.
Overall it's a tough sell for thermal storage as a means of handling renewables intermittency. As we've seen, thermal storage sets efficiency against grid regulation. Generally, when we have schemes with competing criteria they fail to be economically attractive. Witness my investigation into solar thermal cooling. In that case there was a competition between the efficiency of the solar thermal collector and absorption chiller on the basis of temperature. Here we have competition on pure power. Yes, we can store off-peak power, but the effective round-trip efficiency is going to be unimpressive simply due to the drop of in performance of the heat pump.
There is still the possibility to run numerous appliances on a deferrable basis. Heat, air-conditioning and refrigeration all only need to maintain a given (if narrow) temperature range so with good insulation they should be able to run on relatively short duty cycles. Other appliances, such as the dishwasher or combination washer/dryer can be scheduled.
Chicken or Egg?
One problem with pumping efficient homes is that houses last for such a long time. One often heard meme in the peak oil world is that car fleets take too long to be replaced. Houses can be renovated, cars can't. Still if you are one of those people who think suburbia is evil (as opposed to just soulless) then the choice of whether to concentrate on improving the efficiency of houses or cars presents quite a quandary. From my point of view, I'm more concerned overall with climate change and more localized pollution of the air and water. If people want to live in rows of identical pink stucco houses... enjoy.
04 June 2006
Soy Biodiesel Review
The topic of discussion is Sheehan, J., V. Camobreco et al. (1998) . Life Cycle Inventory of Biodiesel and Petroleum Diesel for Use in an Urban Bus. Golden, National Renewable Energy Laboratory. It's a big, inclusive report (314 pages) on the the energy balance of soy derived biodiesel and fossil diesel.
Energy Return
Let's start on p. V of the executive summary:
Fortunately, the results are not that badly off due to this factor. The study divides the production of biodiesel into five stages:
I went through the study to attempt to figure out what the difference was between fossil and absolute energy inputs. Annoyingly, for Stage 4 (Conversion), the energy of the soy oil is incorporated as an input. What makes this frustrating is that the authors at no point in the study actually define what they consider the energy content of soy oil to be, which makes deconstructing this part of the study difficult.
Table 1: Energy Allocation to Biodiesel Production Stages
As it happens, I get a better result (3.24 > 3.2) but that's due to the fact that I employ the Higher Heating Value -- the original authors' calculation uses the LHV. As it happens, this is only a minor bone I have to pick with the study. The big problem is with what's called "Allocation of Lifecycle Flows." Anyone who has read into ethanol studies will know this as 'coproducts'.
Funny Coproduct Accounting
The first giant problem associated with 'coproducts' appears in the Separation (or crushing) stage. The oil content of soybeans is rather low − around 18.4 %. For this entire study, allocation of energy consumption between biodiesel and coproducts is done purely on a mass basis. Unfortunately, this leads to a silly assumption. Table 82 (p. 136) allocates 18 % of energy consumption for the Separation stage to soy oil and 82 % to meal. This in turn propagates back through the allocations for transport and agricultural energy consumption. Is this fair? Take a look at Table 64 (p. 121):
Table 2: Mass composition of soybeans
That's right boys and girls, the authors are allocating the same value to oil as dirt and water. Realistically if the mass of dirt, water, and hulls were discarded then the oil would have to assume 24.2 % of energy use for the first three stages. Furthermore, it probably makes more sense to compare the ratio between the wholesale price of soy oil versus soy meal to determine the proper value of the coproducts. Free hint: the oil is worth more per kilogram than the meal.
This process is repeated for the Conversion stage is similar for the allocation between methyl ester (biodiesel) and glycerin. For this stage, 82 % of the energy is allocated to biodiesel and 18 % to glycerin. Once again this allocation is propagated back through the previous steps. However, this calculation is actually unfavourable to the biodiesel. Separating the glycerin and excess methanol consumes approximately 65 % of the energy for the Conversion stage (Table 96, p. 159). The reason is distillation. As anyone who has looked at ethanol systems will know, distillation is a killer because it requires so much energy to vapourize water. Also, the NREL numbers come out quite high compared to some European plants also presented in the report.
From my point of view, I want to know if biodiesel is energy positive, regardless of coproducts. For soy, the answer appears to be no. Going back and removing the coproduct credits appears to give the following results:
Table 3: Energy Consumption for Biodiesel Production
with Zero Coproduct Credits
Before we all fall into a state of depression, it is fairly clear from the report that there is a lot of promise in reducing the energy inputs for the conversion stage. Methanol inputs constitute approximately half the energy inputs. I have previously hypothesized that anaerobic digestion of the meal could produce methane which in turn could be made into methanol in addition to providing heat energy. The NREL numbers require approximately three times as much energy as some quoted European operations (Table 98, p. 161).
There are potential improvements to be made to the efficiency of the Conversion stage as well. Research and development on catalysts offers the potential to reduce the reaction temperature. In particular I think a zeolite could be ideal for separating the glycerol from the methyl ester chains. Most of the energy (65 %) is used not for the actual conversion but for distilling out glycerin and excess methanol post-transesterfication − normally an excess of methanol is added to carry through the reaction to completion. Reducing the amount of water and methanol used will have a direct result on the distillation requirements.
Like ethanol, biodiesel would benefit significantly from combined heat and power generation. The temperature requirements for most processes is low enough (50 - 70 °C) that the use of solar thermal systems to augment the heat production is feasible.
To a certain extent glycerin might be the biodiesel analogue to sulfur for petroleum oil. Sulfur is a chemical with its uses, but oil refining produces mountains of the stuff. Will glycerin be a product worth distilling in a biodiesel nation, or should it just go into the anaerobic digester to make more methane?
Soy versus Rapeseed (Canola)
Any way you cut it soy is not an ideal crop for biofuel production. Soy does have one significant advantage in that it's a legume and hence fixes atmospheric nitrogen. As such, the energy requirements for fertilizer for soy is very low compared to everyone's favourite biomass villain, corn. However, the foremost quantity on my mind is the low oil content of soybeans. It's about 18 % (Table 64, p. 121) versus 40 % for rape and jatropha or 70 % for coconut. Rape appears to be the best temperate crop for biodiesel production. Its oil quality is high as its content, and its moisture content low.
The NREL study uses an average yield of 36 bushels/acre for soy which works out to 445 kg (oil)/hectare. (Here is a useful webpage for converting agricultural units from US Customary nonsense to more sensible metric units. Oh, and soybeans are 60 lbs./bushel, not 56 or 48 or 25 lbs./bushel but you all knew that, right? Next thing you know they'll be measuring the volume of biodiesel in barrels.) In comparison Canadian Canola yields about 640 kg (oil)/ha. The same source gives European Rapeseed a much higher yield of approximately 1280 kg (oil)/ha, largely due to the greater use of irrigation.
Aside from the oil content issue there are a number of other drawbacks for soy. For the most part, soy appears to take a great deal of work to get the oil separated from the meal. Soy has a high moisture content of 16.0 % water by mass (Table 64, p. 121) which necessitates drying.
In comparison, Canola is about half that if properly sun dried, and hence can be processed without drying. Soy also needs to be flaked into regular sized small pieces, which constitutes about a quarter of the electricity requirements for the Separation stage.
Energy Return
Let's start on p. V of the executive summary:
Biodiesel yields 3.2 units of fuel product energy for every unit of fossil energy consumed in its life cycle. The production of B20 yields 0.98 units of fuel product energy for every unit of fossil energy consumed.That first number, 3.2 units of fuel product energy for every unit of fossil energy. What does this mean? It's in a big bold block quote in the executive summary. It looks like the EROEI, right? Unfortunately it's not. On p. 207 we find that Fossil Energy Ratio = Fuel Energy/Fossil Energy Inputs. In other worlds, any power input that is not a fossil source is not accounted for. For the purposes of this study, this means the hydroelectric and nuclear power share. What we actually want to know is the total process energy required. The energy inputs for biodiesel are predominately electricity (to run machinery) and low grade steam (50 - 70 °C), along with natural gas (to produce methanol) in addition to the standard farm inputs.
Fortunately, the results are not that badly off due to this factor. The study divides the production of biodiesel into five stages:
- Agriculture
- Transport from farm to processing plant
- Soybean crushing and oil separation operations
- Conversion of soy oil to methyl ester fuel.
- Transport and distribution of biodiesel to consumers.
I went through the study to attempt to figure out what the difference was between fossil and absolute energy inputs. Annoyingly, for Stage 4 (Conversion), the energy of the soy oil is incorporated as an input. What makes this frustrating is that the authors at no point in the study actually define what they consider the energy content of soy oil to be, which makes deconstructing this part of the study difficult.
Table 1: Energy Allocation to Biodiesel Production Stages
| Activity | Energy (MJ/kg biodiesel) | Source |
| Agriculture | 3.158 | Table 62, p. 116 |
| Transport | 0.162 | Table 63, p. 118 |
| Separation | 3.471 | Table 83, p. 137 |
| Conversion | 5.572 | Table 105, p. 166 |
| Distribution | 0.162 | Table 106, p. 169 |
| Total | 12.526 | |
| Higher Heating Value | 40.6 | Table 108, p. 173 |
| Lower Heating Value | 37.0 | Table 108, p. 173 |
| ERR (HHV) | 3.24 | |
As it happens, I get a better result (3.24 > 3.2) but that's due to the fact that I employ the Higher Heating Value -- the original authors' calculation uses the LHV. As it happens, this is only a minor bone I have to pick with the study. The big problem is with what's called "Allocation of Lifecycle Flows." Anyone who has read into ethanol studies will know this as 'coproducts'.
Funny Coproduct Accounting
The first giant problem associated with 'coproducts' appears in the Separation (or crushing) stage. The oil content of soybeans is rather low − around 18.4 %. For this entire study, allocation of energy consumption between biodiesel and coproducts is done purely on a mass basis. Unfortunately, this leads to a silly assumption. Table 82 (p. 136) allocates 18 % of energy consumption for the Separation stage to soy oil and 82 % to meal. This in turn propagates back through the allocations for transport and agricultural energy consumption. Is this fair? Take a look at Table 64 (p. 121):
Table 2: Mass composition of soybeans
| Oil | 18.4 % |
| Dirt | 0.8 % |
| Hulls | 7.4 % |
| Water | 16.0 % |
| Meal | 57.4 % |
That's right boys and girls, the authors are allocating the same value to oil as dirt and water. Realistically if the mass of dirt, water, and hulls were discarded then the oil would have to assume 24.2 % of energy use for the first three stages. Furthermore, it probably makes more sense to compare the ratio between the wholesale price of soy oil versus soy meal to determine the proper value of the coproducts. Free hint: the oil is worth more per kilogram than the meal.
This process is repeated for the Conversion stage is similar for the allocation between methyl ester (biodiesel) and glycerin. For this stage, 82 % of the energy is allocated to biodiesel and 18 % to glycerin. Once again this allocation is propagated back through the previous steps. However, this calculation is actually unfavourable to the biodiesel. Separating the glycerin and excess methanol consumes approximately 65 % of the energy for the Conversion stage (Table 96, p. 159). The reason is distillation. As anyone who has looked at ethanol systems will know, distillation is a killer because it requires so much energy to vapourize water. Also, the NREL numbers come out quite high compared to some European plants also presented in the report.
From my point of view, I want to know if biodiesel is energy positive, regardless of coproducts. For soy, the answer appears to be no. Going back and removing the coproduct credits appears to give the following results:
Table 3: Energy Consumption for Biodiesel Production
with Zero Coproduct Credits
| Activity | Energy (MJ/kg biodiesel) |
| Agriculture | 21.40 |
| Transport | 1.10 |
| Separation | 23.52 |
| Conversion | 6.80 |
| Distribution | 0.20 |
| Total | 53.01 |
| ERR (HHV) | 0.766 |
Before we all fall into a state of depression, it is fairly clear from the report that there is a lot of promise in reducing the energy inputs for the conversion stage. Methanol inputs constitute approximately half the energy inputs. I have previously hypothesized that anaerobic digestion of the meal could produce methane which in turn could be made into methanol in addition to providing heat energy. The NREL numbers require approximately three times as much energy as some quoted European operations (Table 98, p. 161).
There are potential improvements to be made to the efficiency of the Conversion stage as well. Research and development on catalysts offers the potential to reduce the reaction temperature. In particular I think a zeolite could be ideal for separating the glycerol from the methyl ester chains. Most of the energy (65 %) is used not for the actual conversion but for distilling out glycerin and excess methanol post-transesterfication − normally an excess of methanol is added to carry through the reaction to completion. Reducing the amount of water and methanol used will have a direct result on the distillation requirements.
Like ethanol, biodiesel would benefit significantly from combined heat and power generation. The temperature requirements for most processes is low enough (50 - 70 °C) that the use of solar thermal systems to augment the heat production is feasible.
To a certain extent glycerin might be the biodiesel analogue to sulfur for petroleum oil. Sulfur is a chemical with its uses, but oil refining produces mountains of the stuff. Will glycerin be a product worth distilling in a biodiesel nation, or should it just go into the anaerobic digester to make more methane?
Soy versus Rapeseed (Canola)
Any way you cut it soy is not an ideal crop for biofuel production. Soy does have one significant advantage in that it's a legume and hence fixes atmospheric nitrogen. As such, the energy requirements for fertilizer for soy is very low compared to everyone's favourite biomass villain, corn. However, the foremost quantity on my mind is the low oil content of soybeans. It's about 18 % (Table 64, p. 121) versus 40 % for rape and jatropha or 70 % for coconut. Rape appears to be the best temperate crop for biodiesel production. Its oil quality is high as its content, and its moisture content low.
The NREL study uses an average yield of 36 bushels/acre for soy which works out to 445 kg (oil)/hectare. (Here is a useful webpage for converting agricultural units from US Customary nonsense to more sensible metric units. Oh, and soybeans are 60 lbs./bushel, not 56 or 48 or 25 lbs./bushel but you all knew that, right? Next thing you know they'll be measuring the volume of biodiesel in barrels.) In comparison Canadian Canola yields about 640 kg (oil)/ha. The same source gives European Rapeseed a much higher yield of approximately 1280 kg (oil)/ha, largely due to the greater use of irrigation.
Aside from the oil content issue there are a number of other drawbacks for soy. For the most part, soy appears to take a great deal of work to get the oil separated from the meal. Soy has a high moisture content of 16.0 % water by mass (Table 64, p. 121) which necessitates drying.
In comparison, Canola is about half that if properly sun dried, and hence can be processed without drying. Soy also needs to be flaked into regular sized small pieces, which constitutes about a quarter of the electricity requirements for the Separation stage.
01 June 2006
Energy Return on Energy Invested (EROEI)
The energy return on energy invested − abbreviated EROEI − is commonly used to describe the net energy gain for an energy system normalized by the input. This can be applied to many renewable systems in a straight-forward manner or to the full lifecycles of biofuels, nuclear power plants, etc. Mathematically, EROEI is defined as,
Since the error in definition is pretty widespread I don't think there's any point to trying to combat it. I don't bother and I freely call the energy return ratio, EROEI. Still it's useful to keep in the back of your mind. If it does bug you just use ERR and try to remove EROEI from the vocabulary. On the other hand, if you want to use EROEI to model exponential growth, you better use the EROEI rather than the ERR or you'll get a wrong answer.
I don't mean to be pedantic on the subject but I need to make this clear because I've been looking at NREL's soy biodiesel study and there's some funny definitions going on.
EROEI = ΔE / Ein = (Eout - Ein) / EinSimplifying yields,
However, as most of you are probably aware when you see a listed EROEI number the above equation isn't what's used. What you actually are typically given is the Energy Return Ratio (ERR).EROEI = Eout / Ein − 1
Obviously the two are quite similar except for the -1 in the definition for EROEI. If you've ever heard, for example, that the EROEI (actually ERR) of corn ethanol is 0.87 and that's 'negative' you may not have quite understood. On the other hand, if you use the proper EROEI definition then an ERR 0f 0.87 is an EROEI of -0.13. For ERR the break-even point is 1 while it's 0 for to proper definition of EROEI.ERR = Eout / Ein
Since the error in definition is pretty widespread I don't think there's any point to trying to combat it. I don't bother and I freely call the energy return ratio, EROEI. Still it's useful to keep in the back of your mind. If it does bug you just use ERR and try to remove EROEI from the vocabulary. On the other hand, if you want to use EROEI to model exponential growth, you better use the EROEI rather than the ERR or you'll get a wrong answer.
I don't mean to be pedantic on the subject but I need to make this clear because I've been looking at NREL's soy biodiesel study and there's some funny definitions going on.
Subscribe to:
Posts (Atom)