Archive for the 'green' Category

Windy isn’t it?

2009-09-09

Damn hippies think we can just sprinkle a few wind mills around, and because Europe has “huge wind resources” we’ll be okay.

This silly web article claims that europe’s wind energy potential is “huge”, and “equivalent to almost 20 times energy demand in 2020”.

O RLY?

YA RLY, according to the European Environment Agency’s report, Europe’s onshore and offshore wind energy potential.

O RLY?

YA RLY: It’s hard to miss this sentence from the executive summary: “Europe’s raw wind energy potential is huge. … it may be equivalent to almost 20 times energy demand in 2020”.

“energy demand”, that’s the problem. Their assumed energy demand is between 3537 TWh and 4078 TWh. (By the way, notice that the EEA cover their backs with a “may” when they use the lower demand figure to get the “20 times” headline-grabbing numbers, but the web article referencing somehow manages to drop the “may”). So, Europe has 271e6 people (according to Google); that’s 15.3 kWh per person per day. Oops. They must have meant…

Electricity demand.

Twats.

The electricity demand, in Europe, in nothing like our energy demand. In the UK we travel around by burning oil, and we heat our houses and food by burning gas. That hugely swamps our electricity usage.

Energy and Electricity are not the same thing.

Double twats for the people who ignorantly repeated them. Of course the European Environment Agency know the difference. There are two occurrences of the phrase “energy demand” in the document; 7 occurrences of “electricity demand”. Both the “energy demand” phrases related to the “20 times” sentence. One is in it, the other is in the footnote of the table of data on the same page as the “20 times” sentence. Before I did the textual analysis (by which I mean I used the PDF search feature; it’s abysmal, but it’s what I have available) I put the use of “energy demand” down to sloppy practice. Now I think it’s mischievously deliberate. I think they used “energy demand” in that “20 times” sentence in the executive summary because they knew people would make a headline of it.

I have to say that apart from this headline grabbing glitch, the report is well worth reading. Map 6.1 is particularly interesting (apologies for the pixelly rendering, partly their fault, partly mine, but mostly the fault of STOOPID PDFs):
Cost of wind in europe

Basically the British Isles is the only place in Europe (not quite, but nearly so) with cheap on-shore wind. And we’re full of NIMBYs.

Food Chain Emissions

2009-07-13

Friends of the Earth have sent our household a postcard. It says «The meat and dairy industry produces more climate-changing emissions than all the planes, cars and lorries on the planet.» They don’t quote a study, or any other source. Just a bold assertion which, on the face it, seems implausible. Even if you eat a gargantuan 250 g of meat a day (in other words, the typical US diet; Europeans eat about half that), does that really compare to all that driving round? It also seems a little bit mean to exclude trains and ships on the “transport” side. Is the balance between transport and food really so close that those 2 modes make all the difference? In the UK, rail and water account for about 4% of the total transport energy budget, so I would hope that the question isn’t so close that adding them back in tips the scales the other way. For one thing, any reasonable quantification of errors is bound to swamp that.

I think the FoE statement is false, here’s my homework.

David MacKay stacks up the UK’s energy consumption (Sustainable Energy – Without the Hot Air, Chapter 18, page 103), he has (per person): car 40 kWh/d, plane 30 kWh/d, food 15 kWh/d. So with 70 kWh/d (82 if we add the other transport modes) on the side of transport, and 15 kWh/d on the side of food then it does indeed seem implausible that food chain emissions would be higher. Note that we have all food production on one side, I can’t be bothered separating out meat from the rest, clearly meat forms the bulk of the energy consumption anyway. But wait…

As well as emissions related to the energy required to maintain the animals, they produce carbon-dioxide and methane all by themselves. In other words the food industry has emissions not related to its energy inputs (even if all the energy was produced sustainably, there would still be emissions). Non-energy related emissions show a weakness in David MacKay’s book; he neglects them completely. That’s okay, because his focus is Sustainable Energy, but be aware that it’s not the whole picture. Food, concrete, deforestation all have non-energy emissions. For animals I think we can neglect the CO2 emissions because the carbon originally came from the atmosphere anyway (respiration forms part of a close carbon cycle). Methane however is not negligible.

I reckon 1 kg of lamb produced between 60 g and 180 g of methane when it was walking about in the Peak District. That’s equivalent to about 2.4 kg of CO2. Let’s say I eat 100g of lamb a day. That’s (methane emissions equivalent to) emissions of 240g CO2, or about 1kWh of diesel. That’s roughly 0.1 litres; if you fill up 40 litres (about the size of my small car’s tank) every two weeks then that’s 3 litres a day. How often do you fill up? From a personal perspective, It looks like food-related methane emissions are not even close (to transport emissions).

Okay. So much for the ovine. What about the bovine, porcine, and, er, chickens? Well, I’m no veterinarian so this will take a lot of piecemeal research. Bugger that, lets go to a (competent?) summary: The UK’s Fourth National
Communication under the United Nations Framework Convention On Climate Change
. In 2004 UK agriculture (note: not just meat and dairy) emitted 13.8 MtC (megatonnes of carbon equivalent); transport emitted 37.4 MtC. Just what are these Friends of the Earth smoking that makes them think they can claim “The meat and dairy industry produces more climate-changing emissions than all the planes, cars and lorries on the planet” when it is so out of line with the UNFCCC GHG inventory. Is the UK really so atypical?

I suspect that what’s really happening is that the FoE are doing some clever accounting. There’s probably a little bit of double accounting (example, counting transport of feed on both sides), and I suspect some land use change. Perhaps they include chopping down ancient forest to grow soya beans for animal feed as an emission on the food change? I just don’t know, because they don’t show their homework. But I have a couple of points to make anyway. The first is that it’s not at all clear that the beef industry is too blame. If there was less demand for beef (and hence soya beans to feed the cows), then I think it’s likely that the same companies would have chopped down the same forest to grow something else. Miscanthus perhaps. The second is that while this land use change will be an emission (the UNFCCC recognises land use and land use change as a carbon source / sink), this emission occurs only once. Once the forest is cleared to grow soya, there will be no land use change emissions. So the emissions from the single land use change should be amortised over all future soya bean seasons. I think.

So FoE, how do you make the sums add up?

Appendix for the pedantic

«250g of meat a day … the typical US diet»

A quote from USDA Agriculture Factbook 2001-2002, Chapter 2, “Profiling Food Consumption in America”, http://www.usda.gov/factbook/chapter2.htm :

“In 2000, total meat consumption … reached 195 pounds … per person”. That’s 242 g per person per day (2000 was a leap year).

«rail and water account for about 4% of the total transport energy budget»

Department for Transport, TSGB Chapter 3: http://www.dft.gov.uk/pgr/statistics/datatablespublications/energyenvironment/

«1kg of lamb produced between 60g and 180g of methane»:

One 60 kg ewe produces about 20 litres methane a day (see below). Boned and trimmed meat is about 2/3 of the animal’s weight, so 0.5 litres / kg (boned). Lamb is generally defined as less than 12 month’s old or less than 18 month’s old for export. 360 days × 0.5 litres = 180 litres. × (the density of methane gas) 0.717 g/l = 129 g. 60 g to 180 g gives a range around this (to account for younger and older lambs, for one thing).

«one 60 kg ewe produces about 20 litres methane a day»

See Proceedings of the Nutrition Society, Volume 41, page 9A, meeting of 1981-07-17, “Methane production in lambs fed high- and low-roughage diets”. It depends on their diet: about 23 litres for high roughage; about 9 litres for low roughage. Two things: 1) when did you last see sheep being fed lucerne hay? 2) using 20 litres per day favours the FoE case anyway.

«equivalent to about 2.4 kg of CO2»

In terms of greenhouse gas warming potential, per kilo, methane is 20 times more potent than CO2. So 120 g methane equivalent to 2.4 kg CO2.

Four candles!

2009-03-31

A hilarious blunder in my previous article about candles has me out by a factor of 10 on the calorific value of candles. In that article I said wax has about the same calorific value as butter, 3 kJ/g. It turns out that the calorific value of butter is about 30 kJ/g. Oopsie.

That means one modest candle burns at 75 W (not 7.5) and four candles burns at a whopping 300 W! So if you lit any candles then you were probably emitting more carbon than the “business as usual” scenario of having a couple of lights on.

This more or less confirms my prejudices that Earth Hour was a pointless and futile gesture so you could be seen to do something, without actually having to bother to go carbon free.

Secrets of Reducing Your Carbon Footprint

2007-04-23

Can we grow willow and bury it?

This carbon footprint article from The Independent reckons that the average Briton’s carbon footprint is 10.92 tons of CO2.

This article about phytoremediation in Sweden suggests short rotatation coppicing gives a yield of about 6-12 tonnes of oven-dried willow per hectare per year. Similar yields in England are suggested by the survey results that I got Ian Tubby of the Forestry Commission’s Biomass Energy Centre to e-mail me. Optomistic rule of thumb: 10 tonnes of willow per hectare per year.

Willow is about 50% carbon. So from one hectare we can sequester 3-6 tons of carbon.

That seems like a long way off the 10.92 tons of CO2 that we’re each responsible for producing. But hold onto your apples and oranges there. A little bit of chemistry reveals that 1 ton of carbon is equivalent to 3.67 tons of CO2. That’s because carbon has atomic weight 12, but CO2 has molecular weight 44 (12+16+16), so every 44 tons of CO2 has only 12 tons of carbon in it.

So our 10.92 tons of CO2 per year is only 2.98 tons of carbon. Which we can easily offset with 0.6 hectares of willow or so. Of course to actually offset the carbon we need to bury the willow. In a hole in the ground. Like maybe a coal mine. (And how do we replace the P, N, and K that I’ve just buried?)

Of course as well as sequestering carbon to offset my footprint I could displace carbon. Instead of burning coal (geological carbon) I could burn willow. This leaflet from some random consultants suggests that 0.7 hectare of willow is sufficient to heat a 3 bedroom house.

Anyone know the average number of KWh per year it takes to heat a house in the UK? It’s surprisingly hard to find the answer in anything approaching an SI unit. This so obviously transient page (referenced on 2007-04-20) links to dataset ST341114 from the Office of National Statistics. That gives a 2001 figure of 1210 for space heating and 450 for water heating. Per household. The units? Why, kilograms of oil equivalent of course (haven’t these guys heard of SI?). Which Wikipedia suggests is a bit of a variable quantity; 1 kilogram of oil equivalent could be 42, 41.868, or perhaps 41.85 MJ. Really I only need a rough guide. Call it 42. That’s 69.72 GJ per jear.

Plausibility check: I burn about 1.2 tonnes of anthracite a year, plus some electricity to heat water in the summer. Anthracite has calorific value of 36 MJ kg-1 so that’s 43.2 GJ plus the electricity. So we’re in the right ball park. An even cruder check would be that 1.2 tonnes of coal is surely about the same amount of heat as 1.2 tonnes of crude. This time I’m thankful that the ONS uses silly non-SI units.

Seasoned wood has a calorific value of 16 MJ kg-1. The average household will need 69.72/16 = 4358 Kg of seasoned willow. About 0.5 hectare then (and a 5-year lead time (3 for growing up to the first harvest, 2 for seasoning), eek!). So the random consultants are in the same ball park with 0.7 hectare. There are 2.4 people per household so we only need 0.2 or 0.3 of a hectare per person to displace the carbon we were using for heating (which, according the The Independent article, is .40 tonnes). The lower calorific value of willow (compared to anthracite or crude) means we need to grow more willow, but we end up burying less.

So by swallowing a few assumptions, I personally could make myself carbon neutral with less than a hectare of willow. Unfortunately the UK has only 24 million hectares of land (and no, we’re not going to be growing willow on all of it). What are the rest of you going to do?

Still, it was a nice thought experiment.

The sorry state of science reporting

2007-04-02

Like many independent thinkers, I’ve come to realise that reporting is rubbish. Science reporting in particular. Probably all reporting, but I like to think that I know a tiny bit about science, so I can spot the poor reporting more easily. Take this BBC article:

EU biofuel push ‘to ruin forests’

The headline is “EU biofuel push ‘to ruin forests'”. Then we read “Oil firms have warned that European Union plans on biofuels could wreck the world’s rainforests.”

So the news article is really an “anti bio-fuel” piece written by Big Oil. Big Oil is down on bio-fuel because you can grow it instead of drilling for it. Big Oil likes LPG and hydrogen because you can make those from crude. Imagine if cars ran on straight vegetable oil, you could grow it in your back yard! You can see why Big Oil might be a bit scared by that. Of course I don’t mean to say that Big Oil literally wrote the piece, but I mean that Big Oil hired a Respectable PR Company to write a Press Release which they put on the BBC editor’s desk and then passed to a sub who changed a couple of adjectives, rang a Rent-a-Quote and slapped it on the website. That seems to be how news is done these days.

Is this was a proper news article then I would expect to see a few sources. Who are these “oil firms”, as in “oil firms have warned …”? We just don’t know. You see how this is used to lend an air of credibility to the piece without actually having information that can be independently verified? Later on “one government official told the BBC: ‘The policy is running ahead of the science … ‘”. A government official? With a name? From what department? In what capacity did he tell the BBC this? Pure flak. Again, no verifiable information.

You can always tell where a sub has been. Consider this paragraph: “Experts agree it makes sense to maximise wood waste and to grow energy crops on land that is marginally productive for food.” The nameless experts of course provide filler without leaving a verifiable trail. But what does “maximise wood waste” mean? Perhaps before the sub came along it said “maximise biofuel production from wood waste” or something that actually made sense. Who knows. (Aside: wouldn’t it be better to sequester the carbon in wood waste and simply bury it?)

Again faceless experts are called in: “Many biologists warn there is simply not enough land on the planet … “.

Next up is an explanation that we’re supposed to take as given: “Already President Bush’s highly-subsidised drive to get fuel from the Prairies has triggered food riots in Mexico because it has pushed up the price of corn.” There’s no reference to any research or paper (or even a rent-a-quote) that claims that the riots were caused by the farming subsidies. No critical eye has been applied, just a bland “reprint whatever the press release says” approach. Are there any other possible causes? Is it possible that the riots were caused by trade agreements between Mexico and the USA? Or that the Mexican people are using this issue to protest at their government? There’s simply no investigation of alternative explanations. Big Oil says bio-fuel is bad because it causes riots, so that’s what goes to press.

Towards the end of the article we get to some quantitative blindfolding: We see that the UK government wants to produce 20% of electricity from renewable resources, but that the EU wants 20% of all energy to come from renewables. The article points out that since electricity accounts for about a quarter of all energy then that’s four times as much energy from renewables (than the UK government had in mind). Close, but no banana. What about approaches that involve producing less energy overall? If we produce less energy overall then that’s less renewable energy also. A sound article would at least mention this possibility including strategies of more energy efficient housing, more energy efficient cars, mass transport policies, aviation tax, and so on. In this BBC article? Simply not on the agenda. Of course the proportion of renewable energy is still four times higher (in the EU position versus the UK position), but the total need not be. (Aside: it’s totally bogus to set a target as a proportion, but this article isn’t about that debate)

The BBC are not a bad organisation. These days they’re just doing what everyone else is doing. Repeating without thinking. This article again is not a particularly bad article, I’ve certainly seen worse; it just happened to be the one that tipped me over into writing a blog post about bad science reporting. There are lots of example to choose from.

When you see a news article about something that you know about, how often is the article on the mark? Do you suppose that news articles about other things, things you don’t know so much about, are more accurate than those about which you know something?