Earlier this week, the Environmental Working Group, a research and lobby group in DC, released a report on the “environment” and "health" impact of different foods. It found that lamb is the worst offender, followed by grain-fed beef, pork, cheese and farmed salmon.
The report was brought to my attention by a writer at the Huffington Post, who subsequently published this story which includes thoughts on the report a number of outside experts on the issue. I commented on the climate impacts of feed production and the logic of farming top-of-the-food chain fish like salmon, both issues that have been discussed frequently here at Maribo.
Here's a more complete list of my thoughts upon examining the short report:
1. “Environmental” impact or “health” impact can be very different than “climate” impact. For example, I’d expect lamb to be much lower on a list based purely on greenhouse gas emissions (i.e. per gram of food produced). I can't comment on "health" impacts as it is not my area of expertise.
2. What I call the “land use cascade” is potentially the largest contributor of greenhouse gas emissions from food production, but also the hardest to calculate. That’s why GHG emissions from dairy relative to beef cattle tend to be overestimated (more methane from dairy cattle, more land required to grow feed for beef than dairy products). It’s also why any study like this should have large positively skewed error bars.
3. All meat is not created equal in terms of greenhouse gases. Grain-fed beef is far less efficient than pork, which is again far less efficient than poultry.
4. If your food choices are motivated purely by concern about greenhouse gas emissions, eating less grain-fed beef is more important than eating locally.
5. Historically-speaking, we are just starting to develop industrial-scale farming of fish, as discussed in the recent Time cover story. Farming the ocean is, in a sense, thousands of years behind farming on land. Right now, many of the choices we are making are, as I put bluntly in the Huffington Post story, “stupid”. Cattle are logical choice for farm animals. They eat grass, so they are only one step away from the sun. Salmon are much higher up the food chain. That’s why many of us say farming salmon is like farming wolves or tigers – you need the whole ecosystem to support the one salmon.
Thursday, July 21, 2011
Climate impact of different foods
Friday, October 23, 2009
Carbon consequences of the biofuels land use cascade
I've written here before about the land use cascade, the sequence of land transformations and land use changes that follow a change in one region.
A new Policy Forum in Science argues that ignoring the cascading carbon consequences of converting lands for biofuels will undercut global efforts to reduce greenhouse gas emissions.
The logic is not new. If croplands and pasture lands are converted to biofuel production, then some other forest or grassland must be cleared to produce the crops or providing the grazing area taken away by the biofuel production. It might happen in the neighbouring county. It might happen on another part of the planet. Either way, it will release soil carbon and plant carbon to the atmosphere (more immediately via burning or later via respiration and decomposition).
The authors argue that we need a new accounting system:
The accounting now used for assessing compliance with carbon limits in the Kyoto Protocol and in climate legislation contains a far-reaching but fixable flaw that will severely undermine greenhouse gas reduction goals (1). It does not count CO2 emitted from tailpipes and smokestacks when bioenergy is being used, but it also does not count changes in emissions from land use when biomass for energy is harvested or grown. This accounting erroneously treats all bioenergy as carbon neutral regardless of the source of the biomass, which may cause large differences in net emissions. For example, the clearing of long-established forests to burn wood or to grow energy crops is counted as a 100% reduction in energy emissions despite causing large releases of carbon.
If it is not fixed, this "accounting problem" has and will continue to cause poor national and international policy decisions.
The Kyoto Protocol caps the energy emissions of developed countries. But the protocol applies no limits to land use or any other emissions from developing countries, and special crediting rules for "forest management" allow developed countries to cancel out their own land-use emissions as well. Thus, maintaining the exemption for CO2 wrongly treats bioenergy from all biomass sources as carbon neutral, even if the source involves clearing forests for electricity in Europe or converting them to biodiesel crops in Asia.
This accounting error has carried over into the European Union's cap-and-trade law and the climate bill passed by the U.S. House of Representatives. Both regulate emissions from energy but not land use and then erroneously exempt CO2 emitted from bioenergy use.
How could it be fixed? The authors argue for a more full and fair accounting of emissions caused by biofuels or bioenergy.
The straightforward solution is to fix the accounting of bioenergy. That means tracing the actual flows of carbon and counting emissions from tailpipes and smokestacks whether from fossil energy or bioenergy. Instead of an assumption that all biomass offsets energy emissions, biomass should receive credit to the extent that its use results in additional carbon from enhanced plant growth or from the use of residues or biowastes. Under any crediting system, credits must reflect net changes in carbon stocks, emissions of non-CO2 greenhouse gases, and leakage emissions resulting from changes in land-use activities to replace crops or timber diverted to bioenergy.
This full accounting is necessary but will be difficult to implement given the uncertainty in soil carbon budgets and the complexity of the land use cascade.
Sunday, May 11, 2008
Shifting diets vs. eating local
I finally had the chance to read this terrific paper by Christopher Weber and Scott Matthews of Carnegie Mellon that compares greenhouse gas emissions from the production different types of food and the delivery of that food to your plate. As was reported by some news agencies and blogs, Weber and Matthews conclude that transportation represents only 11% - on average, it depends on the food – of the total life-cycle GHG emissions of U.S. food (there’s little reason to expect a dramatically different result in Canada).
The take home message is shifting your diet will do far more to reduce greenhouse gas emissions than buying local. From the paper:
The results of this analysis show that for the average American household, “buying local” could achieve, at maximum, around a 4-5% reduction in GHG emissions due to large sources of both CO2 and non-CO2 emissions in the production of food. Shifting less than 1 day per week’s (i.e., 1/7 of total calories) consumption of red meat and/or dairy to other protein sources or a vegetable-based diet could have the same climate impact as buying all household food from local providers.
The authors did some simple calculations to demonstrate this point:
To put these figures into perspective, driving a 25 mi/gal (9.4 L/100 km) automobile 12 000 miles/yr (19 000 km/yr) produces around 4.4 t CO2/ yr. Expressed in this manner, a totally “localized” diet reduces GHG emissions per household equivalent to 1000 miles/yr
(1600 km/yr) driven, while shifting just one day per week’s calories from red meat and dairy to chicken/fish/eggs or a vegetable-based diet reduces GHG emissions equivalent to 760 miles/yr (1230 km/yr) or 1160 miles/yr (1860 km/yr), respectively. Shifting totally away from red meat and dairy toward chicken/fish/eggs or a vegetable-based diet reduces GHG emissions equivalent to 5340 mi/yr (8590 km/yr) or 8100 mi/yr (13 000 km/yr), respectively.
It is important to note that macro-scale GHG “accounting” studies always come with a number of caveats. The calculations or model requires a number of simplifying assumptions and often some more complicated factors are often excluded. The two central limitations to this particular study appear to be the simple treatment of direct GHG emissions from animal and crop production (i.e. N2O from manure, fertilizer and the animals themselves) and the exclusion of land use impacts and the “land use cascade” (i.e. carbon released from directly or indirectly transforming land for crop or animal production). Improving those components of their mode should increase the share of GHG emissions from food production and the relative GHG emissions from red meat production. In other words, that provides even more support for the conclusion that eating less beef is one of the best ways to reduce personal greenhouse gas emissions.
Tuesday, February 12, 2008
Biofuels and the "land use cascade"
As readers of Maribo no doubt heard, two papers in last week’s Science addressed the greenhouse gas emissions that arise from clearing lands for biofuel crop production. It is an important subject that has been widely discussed within the scientific community, including my own collection of colleagues, for the past year or two. You might say these papers are the first to “do the math”. The papers conclude what many carbon cycle experts suspect: that any greenhouse gas benefits that come from using biofuels instead of oil are negated when you include the emissions associated with land clearing.
The publication of both papers at once is enlightening because they tackle slightly different, but complimentary, issues.
Fargione et al. address the direct emissions from the land cleared to plant the actual biofuel crops. The examples includes Brazilian Amazon to soybean biodiesel, Brazilian Cerrado to soybean biodiesel, Brazilian Cerrado to sugarcane ethanol, Indonesian or Malaysian lowland tropical rainforest to palm biodiesel, Indonesian or Malaysian peatland tropical rainforest to palm biodiesel, and US Central grassland to corn ethanol.
Searchinger et al. use a global economic model to look more at the indirect emissions. In the developed world, including Canada and the US , forests or grasslands are not being cleared to plant biofuel crops. Instead, biofuels are being produced on land previously devoted to other crops or from grain diverted from another use (i.e. corn grain goes to the ethanol plant rather than the boat shipping it overseas). The change has a cascading effect on the world market. There is less grain available, which can cause other countries to clear land to feed the market.
I like to call problems like that addressed in the Searchinger et al. paper “land use cascades”. There are countless examples -- one of the my favourites is the effect that the surge in soybean production in the US and Brazil in the 90s had on the Yasawa Islands in Fiji (I tell the whole story is here).
These cascades are becoming increasingly important, and increasingly global in scale. For example, the same thinking needs to be applied to forestry-based carbon credit programs. If a segment of BC coastal rainforest slated for logging is protected, does that mean some other forest must be logged to provide the missing pulp and paper? If so, what effect does that have on the net emissions? We may discover that net greenhouse gas savings only occur if we also reduce demand for the products that would otherwise come from that land either cleared (biofuels) or saved (forest carbon credits). More on that later.
