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« Media blackout | Main | Climate Politics as Manichean Paranoia by Roger Pielke Jr »
Thursday
Sep142017

Biofuels in the 2050 calculator

I've been playing about with DECC's 2050 calculator and I wondered if BH readers (if any of you are still popping by) to take a look at something.

I'm interested in how it handles bioenergy. Here's how the relevant help screen describes the process.

In 2007, the UK used 4000 km2 of land to grow energy crops, which is less than 2% of the country. For comparison, 174 000 km2 of land was used for arable crops, livestock, and fallow land. The 2050 Calculator contains two options relating to agricultural biomass and land use: land use management (described here) and livestock management (described on another page).

In his book, Mackay uses a value of 244,000 km2 for the area of the UK, so "less than 2%" is correct.

Near the bottom of the screen the power output from this 4000 km2 is given at 8 TWh. That's 0.002 TWh/km2, a number that is similar to the value you can derive from the text of the book (24 kWh/person/day, 59,500,000 people, 244,000 km2 gives a value of 0.0028 TWh/km2, and Mackay admits this is optimistic).

Then look what happens when you move the slider for land dedicated to bioenergy. Take Level 4, for example. According to the help text.

Level 4

Level 4 assumes that the UK has a strong domestic bioenergy production focus, with 17% of the country planted with energy crops. There is extensive carbon capture through forestry, and highly effective management and collection of waste materials for bioenergy use. The resulting energy available in 2050 is 545 TWh/y.

Using our figure of 0.002 TWh/km2, 545 TWh will require 272,500 km2 of land. Which is to say pretty much the whole of the UK. 

Can anyone explain why DECC thinks it will only take 17%? Or is my maths wrong somewhere?

Note:

If you want to get to the relevant place on the calculator, start it up, click "Overview" in the bottom left hand corner of the screen and then the "Supply" tab in the top right. Scroll down the list of options on this tab. Near the bottom, you will see "Land dedicated to bioenergy" with a slider that allows you to make your selection. The help screen is available by clicking the "i" button just above the slider. 

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Reader Comments (68)

I bet they assume great technological progress between now and 2050, both for the yield of energy crops and for conversion efficiency.

If you assume that the data are for 2010, and that things get better at 4% per year, acreage falls from 100% to 20% in 2050.

Sep 14, 2017 at 12:21 PM | Unregistered CommenterRichard Tol

It does say “and highly effective management and collection of waste materials for bioenergy use.” So I expect that a large proportion of the energy comes from waste, including waste from imported food and other bio-degradable material.

Sep 14, 2017 at 12:38 PM | Unregistered CommenterBillP

There's a separate slider for energy from waste.

Sep 14, 2017 at 1:07 PM | Registered CommenterBishop Hill

Richard

GM crops then?

Sep 14, 2017 at 1:09 PM | Registered CommenterBishop Hill

Perhaps they've annexed North Carolina, South Carolina and Georgia to grow trees for wood pellets.

Sep 14, 2017 at 1:16 PM | Unregistered CommenterSean

Sean

No, there's a separate line for biomass imports!

Sep 14, 2017 at 1:36 PM | Registered CommenterBishop Hill

I've found the underlying spreadsheet for the calculator.
https://www.gov.uk/government/publications/2050-pathways-calculator-with-costs
If you go to Tab VI.a the first section of orange cells gives the land use for each point on the slider ("Tractories" 1-4). However the figures for each year are hard coded.

But then the 2050 Calculator "How to Guide"
http://ledsgp.org/wp-content/uploads/2015/09/2050-calculator-spreadsheet-how-to-guide.pdf
says this:

Levels 1 to 4 are designed to cover a broad range of possibilities and to test the boundaries of what
might be possible. They are intended to reflect the whole range of potential futures that might be
experienced in each sector. They are illustrative and are not based on assumptions about future
policy and its impacts, and should not be interpreted as such. These levels were agreed following an
extensive call for evidence in Summer 2010 and represent a shared view between the UK
Government, businesses, academics and green groups on the minimum and maximum effort across
sectors.

The shared view of "Government, businesses, academics and green groups" sounds like a recipe for disaster, doesn't it?

Sep 14, 2017 at 1:46 PM | Registered CommenterBishop Hill

Following the trail a little further, I find a report on the call for evidence
https://www.gov.uk//government/uploads/system/uploads/attachment_data/file/42562/216-2050-pathways-analysis-report.pdf

The numbers don't quite match, but there is apparently an improvement in yield of 1.5% per year sourced to a paper by Bauen.
https://www.researchgate.net/publication/45167000_Modelling_supply_and_demand_of_bioenergy_from_Short_Rotation_Coppice_and_miscanthus_in_the_UK

Sep 14, 2017 at 1:54 PM | Registered CommenterBishop Hill

It looks like they are expecting a 7x increase in energy yield per km²

8 TWh from 4000km² = 0.002TWh/km²

599 TWh from 41480km² = 0.0144TWh/km²

They must be expecting great things from CO2 fertilisation.

Sep 14, 2017 at 2:04 PM | Unregistered CommenterTerryS

Actually not. Bauen is the source of the baseline yield of 10 oven dried tons per ha. It currently looks like the growth figure of 1.5% per annum is "think of a number" stuff.

Sep 14, 2017 at 2:04 PM | Registered CommenterBishop Hill

Terry

Yes, almost anything becomes possible with compound growth.

Sep 14, 2017 at 2:09 PM | Registered CommenterBishop Hill

@bish
We have 12,000 years of improving plants for food. We have hardly started with plants for energy. Ditto for the conversion of raw plant material to fuel.

Rapid progress can be expected, but 80% in 30-40 years may be overly optimistic.

Sep 14, 2017 at 2:48 PM | Unregistered CommenterRichard Tol

Richard

Yes, the improvement rate looks rather ambitious set against mainstream crop improvement rates.

Interestingly, the yield improvement rate is different depending how ambitious you are in "going green". i.e. if you go for high levels of bioenergy, you get partial compensation via a better rate for yield growth.

Sep 14, 2017 at 2:55 PM | Registered CommenterBishop Hill

"almost anything becomes possible with compound growth."

33 years of compounded 1.5%/year growth is less than a doubling, not the x7 which TerryS computed.
One needs to compound 6%/year growth over 33 years to effect a multiplication by 7.

Sep 14, 2017 at 5:51 PM | Unregistered CommenterHaroldW

There are some Swedish results:
160 km2 of Salix is reported to possibly produce 0,6 - 0,7 TWh /year in form of woodchips.

Also, using nutrient-rich wastewater increases yield and have a positive effect in water treatment plants.

Sep 14, 2017 at 8:25 PM | Unregistered CommenterBengt Abelsson

I guess it is unlikely that the scrapping of DECC will see and end to facile projects like this.

Sep 14, 2017 at 8:27 PM | Unregistered CommenterDaveS

@bish
So they assumed learning by doing: The more you do, the more you learn, and the better things get.

Empirical evidence is mixed. Wind power expanded so rapidly for a while that anyone who understood how to build a better wind turbine instead focussed on winning as much subsidies as possible (and yes, they learned that doing).

More importantly, technological progress in bioenergy is global, and the rate is largely determined outside the UK.

Sep 14, 2017 at 8:30 PM | Unregistered CommenterRichard S.J. Tol

GOOD TO SEE YOU BACK YOUR EMINENCE!

Sep 14, 2017 at 9:13 PM | Unregistered CommenterSpectator

Think BillP is on to something. It's in the weasel word way they justify Level 4 energy that makes me suspicious.

They may be double dipping and including incremental power (by felling and burning) from the 'carbon capture through forestry' and recycled waste into the total..

Best wishes Bishop

Sep 14, 2017 at 10:25 PM | Registered CommenterPharos

I am not impressed by these models. Back in Jan 2015 the DECC released a revised Global Calculator Model, which I think was referenced here at Bishop Hill. I had a play around and my summary was as follows.

On the 28th January 2015, the DECC launched a new policy emissions tool, so everyone can design policies to save the world from dangerous climate change. I thought I would try it out. By simply changing the parameters one-by-one, I found that the model is both massively over-sensitive to small changes in input parameters and is based on British data. From the model, it is possible to entirely eliminate CO2 emissions by 2100 by a combination of three things – reducing the percentage travel in urban areas by car from 43% to 29%; reducing the average size of homes to 95m2 from 110m2 today; and for everyone to go vegetarian.

In media parlance, the model seemed to have a strong bias to mainstream Progressive, multi cultural, British attitudes, ignoring the cultural sensitivities and aspirations of poorer and less enlightened nations.

Sep 14, 2017 at 11:03 PM | Unregistered CommenterKevin Marshall (Manicbeancounter)

"I wondered if BH readers (if any of you are still popping by) to take a look at something."

Pretty much every d_mn day!

I only read the thread the first few days. Especially if the trollops have shown up in their flimsy attempts to skew the topics.

I also check "NoFrakkingConsensus" and Climate Audit virtually every day. On all three sites, when articles show up, they are well worth reading!

Sep 15, 2017 at 1:53 AM | Unregistered CommenterATheoK

@Bishop: I got here a bit late to see your post, but I do monitor this website pretty much every day - it's one of many websites I subscribe to in my BazQux feedreader, which I scan to see if there is a flag for new/unread posts for each of the websites I watch. I was please to see this post today as your website has long been one of my favourites for good, solid environmental sense and info. I rarely make comments.
Having got here, it seems that you have got answers to your questions and there's probably not much I can usefully add, other than to say that, in my years of working on mathematical models of one sort or another, they fall into two general categories:
(a) Purely data-driven: e.g., a model for North Sea weather - wave height forecasting. The only thing that mattered in this was that the historical logs of observed/measured wave height and prevailing weather conditions (wind speeds, millibars, temps.) be as bang up-to-date as possible, so that the dynamic of any developing seasonal or statistical cycles/trends were able to be used to modify the model's predictions to as close as current-day would permit. This was to plan schedules for barges to supply the North Sea oil rigs in safe weather, avoiding anticipated/predicted dangerous weather conditions.

(b) Assumption-based, using aggregate annualised data: e.g., the UK ITEM Club model (Independent Treasury Econometric Model). This model was largely theoretical, basically an engine driven by a bunch of algebra, into which were fed the known aggregated economic variables (economic performance data). Typically the assumptions posited Best/Median/Worst case scenarios for different industry sectors of the GDP - e.g., (say) that housing building would rise, so this would signal a potential rise in demand for bricks. This was useful for planning production, based on the best information that was available, but it was always governed by the assumptions that were fed into the engine.

Most/all of the climate models are probably of the latter type (b), but veer towards being necessarily highly theoretical due to the lack of understanding/proof as to precisely how climate systems actually work. In such models, the assumptions are of primary importance. For example, the hypothetical assumption/narrative that a rise in the greenhouse gas CO2 is a cause of increased greenhouse average temps. That assumption was rather blasted into pieces when ice core data showed conclusively (but inexplicably) that, historically, CO2 rise seemed to always FOLLOW temp rises, with a lag of about 800 years. Curiously, the prevailing climate models apparently do not reflect the reality of this new data, presumably because it doesn't support the assumption/narrative.

Similarly, DECC's 2050 calculator for biofuels. This would seem to be (as @DaveS observed, above) a facile attempt at a sliderule approach, where little was able to be understood about the thing being modelled (because one did not fully understand the past, and could not predict the future of "biofuel technology"), so the assumptions prevailed, no matter that they had no basis in statistical veracity. They were just guesses, given an air of credibility by dressing them up as some kind of official computer-driven "calculator". A pig wearing lipstick. A cheap sideshow trick, like the charlatan's Hockey Stick climate model.

I have actually worked on such a model (assumption-driven), some years back, which took the aggregates of town gas produced by the then EGB (Enfield Gas Board) and reconciled it with the aggregate revenues (from domestic and commercial users) of the EGB. This had to be done each year, and put into an official annual report of the EGB to British Gas. The only problem was that the aggregates COULD NOT BE RECONCILED (and no-one knew why for sure), so the figures were fudged with made-up values, as the report had to look as though it was official, sane and correct from an accounting perspective.

Yet it was still rubbish - same as (apparently) the DECC 2050 calculator for biofuels.
SOMEONE had to do it. As they say, "I vas just obeying orders". Nevertheless, it got a big fat green tick, and I got paid for it, as no doubt happened with the absurd DECC 2050 calculator for biofuels and its authors.
This kind of rather shameful sleight-of-hand was not, for me, and would not be for for others, the highest point that one would probably aspire to in one's career, really, but politics/bureaucracy were no doubt fully satisfied.

Sep 15, 2017 at 5:07 AM | Unregistered CommenterSlartibartfarst

Slartibartfarst -
(Great name, by the way!)
I appreciate the distinction you draw between type (a) models (deductive) and type (b) models (assumptive/prognostic). I share your mistrust of type (b) models of complex economic & societal systems, this one among many.

However, I would like to address your argument that (to paraphrase) "ice cores show a rise in temperatures prior to a rise in CO2, therefore greenhouse gases do not cause increased temperatures." This is fallacious. There are excellent theoretical reasons to expect that an increase in greenhouse gases will cause an increase in temperature, ceteris paribus. It does, therefore, seem contradictory that while CO2 and temperature both rise during de-glaciation, the temperature begins to rise before CO2.

However, the earth's energy balance involves multiple mechanisms, among which are the effects of orbital variation and of greenhouse gases. In a world in which the concentration of greenhouse gases remains constant, there would still be climatic variation due to Milankovich cycles. What seems to be the case is that as the Northern Hemisphere warms, glaciers retreat, and vegetation occupies the formerly ice-bound land. As plants emit CO2, this increase in vegetation causes the CO2 concentration to rise. The increase in CO2 also causes warming, accelerating the transition to the inter-glacial state.

Whether one accepts the above explanation as generally true or not, it is a plausible example of the inter-connectedness of biological & geological processes. Because of this, one cannot disprove the greenhouse gas hypothesis based only on the observation that a temperature rise occurred without a CO2 rise. One could validly reach such a conclusion only if nothing else could cause a temperature rise, but such is not the case.

Sep 15, 2017 at 6:32 AM | Registered CommenterHaroldW

@HaroldW:
(Good handle you have there, by the way!)
Thankyou for your response to my comments. However, you seem to have somewhat inaccurately paraphrased the words that I wrote, where you say:
"However, I would like to address your argument that (to paraphrase) 'ice cores show a rise in temperatures prior to a rise in CO2, therefore greenhouse gases do not cause increased temperatures'."

That was not what I wrote, nor intended - indeed, it would be difficult to substantiate such a naive/absurd statement - and please don't attempt to put the "wrong" words into my mouth, as it were. Rearranging the words to align with a different/preferred narrative for the sake of argument is not helpful and could be misleading.

The ice core data demonstrated that there was/is a major - and so far inexplicable - disconnect between the observations and the "accepted" hypothesis. When that happens, the data (observations) trump the hypothesis and one thus needs to go back to the drawing-board with the invalid (QED) hypothesis (Feynman). Of course, Feynman - and the scientific method - could have been wrong, I suppose, but it seems to be the best that we have to go on at present, for the pursuit of truth in our understanding of Nature.

I could suppose that the reasons for the climate models not yet reflecting the ice core data - e.g., (say) for what is sometimes called "hindcasting" - is that the climate factors involved which lead to that historical data in the first place are not yet necessarily fully understood. If true, then that could cut two ways - e.g., implying that the factors that contribute to the current planetary/greenhouse warming hypothesis are not fully understood - or at least, not even as well understood as we might have previously thought them to be before we knew of the ice-core data. This could introduce a potentially considerably greater degree of uncertainty, but that would arguably be par for the course - winnowing things down in the pursuit of truth in Nature is like that.

I don't wish to seem discourteous, but, since the rest of what you wrote seems to have been based on, or follows on from a false restatement of what I had written, I shall not expend my cognitive surplus on making any comment on it, but I do appreciate the effort you made.

Thankyou.

Regards,
S.
___________________________________________________

Sep 15, 2017 at 8:17 AM | Unregistered CommenterSlartibartfarst

For a start, it should be noted that food IS fuel; fuel for the organism that ingests it, thus, one could say, Mr Tol, that the centuries of selective breeding (aka genetically modifying) have given us more productive fuels from fewer plants; while one cannot discount the possibility of some radical change, the probability is that this is just another pipe-dream. The pie-in-the-sky dream of powering cars from the same source as our bodies are powered is exactly that – utter hokum! All it will do is drive up the price of food, so impoverishing the majority of the world’s population even more than they are impoverished, now. Perhaps, in the warped, dystopian minds that seem to dream like this, this is the future they want – a world of peasants eking out their lives in subsistence farming, while the elite strut the world, directing the intimate minutiae of the lives of the little people.

We should continue using the solar energy that Mother Earth has thoughtfully collected for us, and rather capriciously storing it such that we do need to look for most of it, to find it in solid, liquid and gaseous forms. With the development of hydraulic fracturing, we have found that our energy requirements will be met by this natural store of solar power for several centuries, yet, so we can ditch our headlong plunge into the madness of renewables, slow it down to a pace at which proper and serious studies of the practicalities of its installation and implementation can be fully and properly assessed – though the evidence to date is that, in its present forms, it is just an utter waste of resources.

All this tosh is predicated upon two erroneous assumptions – that an increase of CO2 will increase global temperatures, and that it is humans who are driving the observed rise in CO2 concentrations. The first of these can be shown to be false – while CO2 concentrations continue to rise, there has been no significant temperature rise for nearly 2 decades. The second can be shown to be flawed, if not out-rightly false, with the first picture released by the OCO-2 satellite, which showed the highest concentrations of CO2 to be over the rain-forests and tropical oceans. This was explained/excused by blaming seasonal burning by subsistence farmers – ignoring the simple logic that, if that was the case, it is a very strong argument for those areas to be industrialised as soon as possible, to lower their CO2 emissions!

Yes, burning the copious quantities of waste that we produce is a good idea – but it should be confined to waste, not to otherwise essential food crops. As so many who advocate this stupid idea claim to be avid environmentalists, could they calculate how much extra wilderness that they claim to be protecting will have to be sacrificed to provide this fuel crop?

Sep 15, 2017 at 10:01 AM | Registered CommenterRadical Rodent

@radical
Current bioenergy indeed directly (corn-based ethanol) or indirectly (wood) competes with food production. Without massive improvements in yields etc, we cannot expect to feed and fuel the world from current croplands.

Note that agricultural land has returned to nature in Europe and North America because we produce more food than we need. Note also that agriculture in Africa and Asia is inefficient, with yield gaps up to 10.

Still, bioenergy at scale will require energy crop production that does not compete with food production, either at sea or in warehouses.

Sep 15, 2017 at 10:22 AM | Unregistered CommenterRichard S.J. S.J. Tol

Richard

Yes, I've been looking at the food angle too. They are assuming food yields of 0.9-1.5% per annum over 40 years. Again, very ambitious!

Sep 15, 2017 at 10:41 AM | Registered CommenterBishop Hill

TerryS

Yes, seven times the energy per km2 in the most ambitious scenarios and four times in one of the intermediate ones.

Sep 15, 2017 at 10:51 AM | Registered CommenterBishop Hill

@Richard S.J. Tol

So they assumed learning by doing: The more you do, the more you learn, and the better things get.

I don't doubt that improvements can be made, but how much?

We have been learning and improving how we grow crops for thousands of years so I doubt there will be a sudden 7x increase in yield in this area over a few decades.

Similarly you could only expect, at most, about a doubling in the energy extracted from the crops as the efficiency is already at 35%. Even this would be overly optimistic.

Sep 15, 2017 at 11:24 AM | Unregistered CommenterTerryS

OK, I've worked it out. In year 1 the biofuels are mostly first generation - ie cereal based - with low TWh/km2. In year 2 and beyond, they switch to Second generation - miscanthus etc - with much higher TWh/km2. So there is an apparent yield boost from the change in mix.

So the number to discuss is actually a near doubling in TWh/km2 for miscanthus etc.

Sep 15, 2017 at 11:33 AM | Registered CommenterBishop Hill

Amusingly, in the RSPB's "2050 vision", they are claiming to get 55TWh from 3500 km2. The implicit rate of 0.0157 TWh/km2 is three times the rate the 2050 calculator suggests is achievable at small levels of biofuels usage and half again as high as the rate it predicts at very high levels of biofuels usage. (As noted above, in Richard's "Learning by doing" comment, higher rates are said to be achievable at higher levels of biofuels penetration).

Sep 15, 2017 at 12:06 PM | Registered CommenterBishop Hill

@guys
I'm not defending DECC's calculator. I'm just trying to work out the assumptions they've made.

As a matter of principle, you should judge a result by the assumptions that led to it.

This is particularly important for long-term projections. Many things that are common in 2017 looked outlandish in 1984. Many things that look outlandish in 2017 will be common in 2050.

That said, while I believe that great strides will be made in bioenergy, I do not think it will go nearly as fast as assumed here.

Sep 15, 2017 at 12:18 PM | Unregistered CommenterRichard S.J. S.J. Tol

Slartibartfarst -
I apologize if I misread your comment. As it's tangential to the topic at hand (DECC model), let's drop the subject.

Sep 15, 2017 at 12:35 PM | Registered CommenterHaroldW

Can't comment on all the maths, but surely there are some logical problems with the "bioenergy" assumptions given the target of getting rid of hydrocarbons.

How are you supposed to grow these biocrops - without hydrocarbons?

Crop yield increases we've seen worldwide are largely driven by - increases in Nitrogenous fertilisers, synthetic pesticides, powered irrigation, improved agricultural machinery and higher levels of CO2 fertilisation. All of these are dependent on hydrocarbons, but just the nitrogen fertiliser via natural gas/haber-bosch process is responsible for 50%(!) of all global food production, the pesticides reduce crop losses by about 30-40%, and CO2 is another 10% growth.

Without the hydrocarbons powering this (or some theoretical replacement)..... food yields would fall from present levels, which means having to take up more space again for food (some estimates say 20% of global land area), which leaves much less space for the biocrops!

Where are these biocrops supposed to grow?

Something not being factored in here is solar/wind etc need enormous amounts of physical space. After you turn up the dials on the calculator to 11 for solar/wind etc, does the amount of space available for the biocrops/food fall enough? The largest solar farm in the entire country (Shotwick) generate a measly 5MW a year and takes up 1 km2. Anyone want to take up 1000 km2 just to get 10% of the UK's electricity?

Sep 15, 2017 at 1:00 PM | Unregistered CommenterMark Tinsley

Following the trail a little further, I find a report on the call for evidence
https://www.gov.uk//government/uploads/system/uploads/attachment_data/file/42562/216-2050-pathways-analysis-report.pdf ... there is apparently an improvement in yield of 1.5% per year sourced to a paper by Bauen

Cherry picked B.S from DECC (not surprising given it was overseen by Chris Hulme at the time, i.e. a proven liar in a court of law). That Bauen paper* cited by DECC provided a constraint of up to 1.5 million hectares for bioenergy use (actually a range of 0.82 - 1.58 million hectares but he went with 1.5m), with the vast majority of crops producing 10-12.5 odt per hectare and almost none above 15 odt.

What is in the DECC paper? Three scenarios:

"Trajectory A": 1.2 million hectares and 15 odt - ~130 TWh produced
"Trajectory C": 2.4 million hectares and 19 odt - ~340 TWh produced
"Trajectory D": 4.2 million hectares and 19 odt - ~500 TWh produced

So 2/3 scenarios blow past the constraints in the paper they've cited as evidence. And to put these make believe fairy world numbers into context, the UK generated 337 TWh of electricity last year from all sources (26 of that from bioenergy, or 7.7%). Oh, so only a 1,800% increase needed for scenario D then.

*And the Bauen paper is nonsense anyway, stating that bioenergy "could" be produced for £12.3 per MWh. Oh really? Start up a bioenergy company and undersell gas, coal, wind and everybody else and make yourself a billionaire then!

Sep 15, 2017 at 1:59 PM | Unregistered CommenterMark Tinsley

Richard is right. You have to judge them on the assumptions made. Their yield growth assumptions are ambitious, and they seem to accept that this is the case.

I'm now looking at the wind farm assumptions, which are equally interesting.

For onshore, they assume they can get 2.5W/m^2, which is odd because David Mackay reckons 2 is as much as you would get onshore and potentially considerably less than that http://withouthotair.blogspot.co.uk/2009/01/power-per-unit-land-area-of-windfarms.html

For offshore, they also assume 2.5, which is on the high side. The latest version of the models assumes that capacity factors will increase to 50% by 2050, which strikes me as absurd.

Sep 15, 2017 at 3:41 PM | Registered CommenterBishop Hill

@bish
Exactly.

Same thing happened in IPCC. In AR4, the conclusion was that the 2K target was out of reach. Assumptions were made more optimistic, and lo and behold, in AR5, the 2K target could be met.

The IPCC is doing a special report on 1.5K at the moment ...

Sep 15, 2017 at 4:47 PM | Unregistered CommenterRichard S.J. Tol

Having studied anaerobic digesters for several years, it is evident that:
1 they don't perform as well as expected
2 the energy required to grow, harvest and transport the crops and to transport and spread the digestate is very similar to the usable energy produced.
3 the amount of land used to grow the crops is enormous, resulting in a very low ratio of energy/area of land.
Certainly the Government has had growing concerns about the "sustainability" of anaerobic digesters that are predominantly fed on purpose grown crops such as maize, grass, wheat, rye and beet.

Sep 15, 2017 at 7:29 PM | Registered CommenterPhillip Bratby

BH: "I've been looking at the food angle too. They are assuming food yields of 0.9-1.5% per annum over 40 years. Again, very ambitious!"

I looked at the trend in yields in the US. Figures for durum wheat, for example, are shown here, pages 215ff. There's been an increase in yields from around 20 bushels/acre in 1960 to around 30 in 2000, to 44 in 2016. An exponential fit to the years 2000-2016 inclusive gives a little better than 2% increase in yield each year.

I'm no expert, so I can't opine on the likelihood of extending the trend another 30 years, but the yield improvement has been on-going for at least 50 years, and remains substantial.

Sep 15, 2017 at 10:17 PM | Registered CommenterHaroldW

@Bish did you Google first ?
Cos I think ppl have already rubbished Decca GiGo 2050 calculator
From July 2015
http://euanmearns.com/the-decc-pathways-calculator-a-false-prophet/

First part of end summary :
"
Time to sum up. Here is an example of how the DECC Pathways Calculator manufactures a pathway to a green, sustainable future that looks good on paper but won’t work in practice, and it’s far from being the only one. In fact no pathway that combines high levels of intermittent renewables generation with inadequate storage is going to work in practice, and because the DECC Calculator conveniently ignores this flaw in its logic it gives results that can only charitably be described as misleading."

Sep 16, 2017 at 12:45 AM | Registered Commenterstewgreen

stewgreen

I'm really only looking at this as an "official" view of land requirements.

Sep 16, 2017 at 9:43 AM | Registered CommenterBishop Hill

@bish
We have 12,000 years of improving plants for food. We have hardly started with plants for energy. Ditto for the conversion of raw plant material to fuel.

Rapid progress can be expected, but 80% in 30-40 years may be overly optimistic.

Sep 14, 2017 at 2:48 PM | Unregistered CommenterRichard Tol


Land plants/trees are the product of thousands of millions of years of evolutionary adaptation and improvement, always fighting to get an extra bang-for-your-buck from available energy (sunlight) and available nutrients. Frankly, I doubt we can get a huge return from making them harvest energy more efficiently. Together with our inputs (mechanical and chemical), farming has benefited from driving plants use of their harvested energy to increase the amount of end product that suits us. It has not increased their overall energetic efficiency and will not do so. I will bet against that every time.

Somebody will then produce a biological example that apparently contradicts me, but their example will fail in the long run once a disease or other natural affliction is taken into the total accounting process. I'll state it again: we can certainly, with some effort, farm nature to produce more products we desire. But farming nature to improve it's overall energetic efficiency is a different ball game. Expect nothing from that venture.

Sep 16, 2017 at 11:47 PM | Unregistered Commentermichael hart

@michael
Plants have optimized themselves for their own benefit, not for ours.

Just compare wild mustard to its crops: http://uk.businessinsider.com/broccoli-kale-brussels-sprouts-vegetables-all-the-same-plant-2015-11?r=US&IR=T

Sep 17, 2017 at 8:26 AM | Unregistered CommenterRichard S.J. Tol

Richard. "Plants have optimized themselves for their own benefit, not for ours". Patently untrue in many cases, as in pipless fruit varieties, or plants designed to produce drugs entirely for our use.

Sep 17, 2017 at 10:54 AM | Unregistered CommenterSupertroll

I think you misunderstood the comment, Minty; plants – as does all life – evolve for their own benefits. Humans have just altered the process so that we may get even more from the plant than it originally was concerned about producing. But, it does raise an interesting question: the drugs that we get from plants are drugs that the plant evolved itself to produce; humans merely discovered them (though we might since have enhanced that) – now, of what benefit is it to a plant to produce these drugs?

Sep 17, 2017 at 4:30 PM | Registered CommenterRadical Rodent

@supertroll
Sorry for being unclear. I should have written "Wild plants" instead of "Plants".

Sep 17, 2017 at 8:18 PM | Unregistered CommenterRichard S.J. Tol

Ravishing R. Actually I was writing about genetically modified plants that produce chemicals totally alien to the plant, but you are correct, plants have also been modified to produce drugs that the plant would normally produce but now in extraordinary amounts.

Richard. Even with wild plants the statement is debatable. Some plants are intimately linked, having co-evolved with animals. For example some orchids have shaped their flowers and nectar to attract specific insects. Are these modifications for the plant? - well yes, but also for the insect. But this is being pedantic, I agree with your statement when it is applied to wild plants. But we were talking about cultivated food and fuel plants.

Sep 18, 2017 at 8:54 AM | Unregistered CommenterSupertroll

With regard to the historical behaviour of temperatures and CO2, attention is nearly always focussed on the times when levels rose - the "lag" of 800 years mentioned above. As there is so much hype today about rising levels, that focus is understandable.
However, in terms of the putative relationship between the two, it is the other side of the hill which is more interesting. At the end of interglacials, while CO2 levels remained high, temperatures fell and the time lag before CO2 followed was much greater - often thousands of years.
I am no expert in this area. If there is a credible explanation consistent with CO2 being the "thermostat", perhaps someone could put it forward?

Sep 18, 2017 at 1:20 PM | Registered Commentermikeh

Mikeh. Yes indeed. Furthermore temperatures fell to levels equivalent to those before the interglacial. What this means is that the high CO2 wasn't able to keep temperatures even minimally above those that occurred in the previous glacial when CO2 levels were minimal. To me this is the best evidence that Quaternary climates were completely independent of CO2 levels - something for lukewarmers to explain.

Sep 18, 2017 at 1:54 PM | Unregistered CommenterSupertroll

I realize that what i wrote may have been confusing. Trying again -
During the previous glacial. Temperatures and CO2 both low.
During the first part of the next glacial (i.e. after an interglacial with high CO2) Temperatures as low as earlier glacial but CO2 remains high.
Thus high CO2 completely unable to ameliorate temperatures during early glacial, thus CO2 greenhouse effect not at all evident. Belief in greenhouse effect requires CO2 to amplify warming during transition to interglacial, but this amplifying effect to become totally ineffective during transition into a glacial stage.

I also mikeh have wondered why this has never really been given more prominence. When I asked at UEA I never received a satisfactory answer. Perhaps we should be asking Entropic Man or Ken.

Sep 18, 2017 at 3:59 PM | Unregistered CommenterSupertroll

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