甲烷效力是二氧化碳的七十二倍
2008.11.12 SMTV訪談澳洲貝瑞·布魯克教授
主持人：環保的觀眾大家好！
在今天的節目裏澳洲阿得雷德大學的貝瑞·布魯克教授將詳述畜牧業對環境的影響。
布魯克教授是研究全球生態學與保育生物學的專家，他擔任休伯特·威爾金爵士氣候變遷基金會主席，也是阿得雷德大學氣候變遷和永續性研究所的所長。他已出版兩本書和一百多篇科學論文，從不同的觀點探討人類對自然環境和生物多樣性的影響。
他曾獲頒澳洲科學院芬納獎章、新南威爾斯皇家學會埃奇華茲·大衛獎章和南澳皇家學會安德列沃斯獎章。
布魯克教授是名列《宇宙》雜誌的澳洲十大青年科學家。
布魯克教授強調人類必須瞭解甲烷是主要的溫室氣體之一。
布魯克教授：甲烷是很有意思的溫室氣體。許多人可能沒聽過，然而它竟是使人類造成氣候變遷的第二大溫室氣體。大家可能都聽過二氧化碳，而甲烷是影響強大且在短期內就舉足輕重的。另一種溫室氣體甲烷主要來自反芻動物、儲藏石化燃料的煤礦和天然氣田也有。例如，油井上方的火，就是燃燒甲烷所致。因此甲烷其實也是天然氣，我們會用以燒熱水等。
我最近和同事完成的某項研究證明，澳洲的全球暖化貢獻，甲烷其實居功厥偉。至少從眼前來看，其他因素都望塵莫及。而製造甲烷的大功臣則是牛、綿羊和山羊之類的反芻動物。他們在消化過程中會產生甲烷。他們咀嚼反芻的食物，而第二個胃裏的細菌會分解植物的纖維素，釋放其中的能量，該過程即所謂的厭氧程式，在無氧狀態下進行，而所產生的甲烷大多經由打嗝釋放。由於甲烷是一種強效的溫室氣體，對氣候變遷影響甚巨，卻多發生在極短的時間內。甲烷十或二十年即消失殆盡，然而若審視那段時間，會發現釋放一噸甲烷等於釋放七十二噸的二氧化碳，因此威力無窮。
根據這個資料澳洲的養牛業、畜牧業、牛、羊，目前每年約排放三百萬噸甲烷。而火力發電廠約排放一億八千萬噸二氧化碳。電廠的全球暖化貢獻似乎遠多於牛的貢獻。然而若仔細想想，甲烷以二十年為期，效力是二氧化碳的七十二倍，再二十年就變成七十二乘以三倍，很容易算出畜牧業在那段時間對全球暖化的影響更甚於火力發電廠，這是澳洲嚴重忽略的事實。
記者：您認為最近給政府的協議書對甲烷輕描淡寫嗎？
布魯克教授：是的，我認為很明顯。不同的溫室氣體對全球暖化有不同的影響，需用某種方法使它們標準化。跨政府氣候變遷小組所用的基本方法是，以一百年為期，取所有氣體的平均值，然而對甲烷而言，其實有點無意義，因為甲烷經過二十年幾乎就消失了，這種方法取其短期的所有影響均分在一百年間，使它的影響大打折扣。這些報告寫甲烷的影響是二氧化碳的二十五倍，然而當它在大氣中發生作用時，其實是七十二倍，是截然不同的。因此我認為那些報告由於那個會計問題，或因許多人不想面對，而對甲烷一筆帶過。如果要嚴肅看待減少碳排的問題，必須說明農業的碳排最重要的，也要說明目前澳洲最大的碳排元兇。
記者：因此若要影響畜牧業，淘汰它，是否有時間處理二氧化碳？
布魯克教授：是的。因為甲烷效力很強，但影響的時間短。諷刺的是，處理甲烷比處理二氧化碳迅速，因此目前雖迫在眉睫，卻是真正可以迅速清除的碳排，無關氣候變遷的理由。
舉例而言，澳洲的羊自九二年起，約從一億九千萬隻減少至一億隻，對澳洲的甲烷排放量影響甚大，是我們可以快速締造改變的例證。基本上只要澳洲的羊排放的甲烷減半即可。對牛也可如法炮製。
而改變公共建設，例如：以替代能源取代火力發電廠，同時又要迅速進行，勢必需要一大筆建設資金。我認為經濟方面比較棘手。反之，減少澳洲的牛只數量卻可迅速完成，只要數年時間，對遏止全球暖化即可立竿見影。
記者：我想回顧您和傑佛瑞·羅素全寫的《肉類的碳足跡》，您能和我們談談嗎？
布魯克教授：好的，我們這份研究在探討家庭吃牛肉所產生的碳排，並與多數人認為更能影響全球暖化的其他活動作比較，我們所舉的例子是福特四輪傳動的一輛休旅車。製造一輛會排放十七噸二氧化碳，每週駕駛每公里會產生兩百克碳排，以此為計算基準。開這輛笨重的車一周會產生六十公斤碳排，還要加上製造時產生的二氧化碳。如果採取"澳洲聯邦科學與工業研究院"所建議的完全幸福飲食法，每週平均吃三至五公斤牛肉，將會發現，即使是以甲烷的效力為二氧化碳二十五倍的標準計算，記住我剛才提過其實是七十二倍的效力，然而即使是二十五倍，每週的碳排也高達二百公斤，比福特四驅車的六十公斤還高。所以只需五年不吃肉，就可彌補四驅車所產生的碳排。這是一例。
另一項探討是生產一公斤牛排所產生的碳排。大量排放的甲烷等於生產一公斤鋁的四倍排放量。生產鋁的過程需經由電解作用，因此極為耗電。牛肉的碳排量多於生產一公斤鋁的四倍，多於開一輛四驅車所排的碳，這些事實都被嚴重忽略。因此這表示，飲食必須有氣候意識，因為生活方式對全球暖化的影響更甚於其他因素。而人們竟渾然不覺。
記者：關於生產牛肉所耗用的水，生產牛肉消耗許多水，您能談談這點嗎？
布魯克教授：好的，的確。生產一公斤牛肉耗用大量的水，生產乳品亦然。澳洲許多乳品業都設在只適合灌溉農副業的土地上，從莫瑞河引水，遍灑廣闊的牧場，以生產足夠的牧草，生產好牛奶，而這卻正是阿得雷德極度短缺的水，使庫龍因供水不足而奄奄一息。水都用以噴灑維多利亞州西部的綠草地，生產乳製品。這種用水方式一點都不明智，因此人們必須瞭解畜牧業的整體影響，體會它們何以危害全球的變遷。當然，從澳洲看到更遠的熱帶，畜牧業是驅使熱帶砍伐森林的主因之一。砍伐森林本身產生的碳排約占所有人為碳排的二成，只為用來放牧牛只。因此畜牧業又是砍伐森林的元兇，伐木燃燒直接排放二氧化碳，然後在那裏養牛，也產生更多甲烷。因此，畜牧業無疑有著長長的陰影，這正是聯合國去年發表的報告標題，內容關於畜牧業對全球變遷的整體影響，影響相當深遠普遍。
記者：您認為政府應更努力讓人民瞭解，如何盡一己之力助地球度過危機嗎？
布魯克教授：我認為遺漏農業碳排等於發出錯誤信號，因為使社會的這部分不必降低碳排。其實社會的每部分都負有責任，如此只是加重其他部分的負擔，而且不正當地承認畜養動物對澳洲環境所造成的影響。人們經常談論氣候變遷的長期影響和本世紀末的情況，然而我們正目睹北極夏冰的消失；熱帶氣候系統的擴展；非洲撒哈拉和澳洲的極度乾旱；預測二、三十年後，五十、一百年後，才會發生的影響，目前卻正在發生，而且我們即將越過美國系統所謂的臨界點，屆時氣候變遷將如脫韁的野馬，或至少會因地球系統的變化而變本加厲，我們正處於決定性的社會臨界點和環保臨界點，該立即行動了!已經刻不容緩!
Professor Barry Brook on Livestock Agriculture and Climate Change
Professor Brook is an international research leader in global ecology and conservation biology. He holds the Foundation Sir Hubert Wilkins Chair of Climate Change and is Director of the Research Institute for Climate Change and Sustainability at the University of Adelaide.
He has published two books and over 100 scientific papers on various aspects of human impacts on the natural environment and biodiversity. He has been awarded the Australian Academy of Science Fenner Medal, Edgeworth David Medal by the Royal Society of New South Wales, and the H.G. Andrewartha Medal by the Royal Society of South Australia. Professor Brook was listed by Cosmos as one of Australia's top 10 young scientists. Professor Brook emphasizes the need to recognize methane as a major contributor of greenhouse gases.
Professor Barry Brook: Methane is an interesting greenhouse gas; many people may not have heard of it, but it’s actually the second most powerful greenhouse gas in terms of human’s total contribution to climate change.
Everyone has probably heard of CO2. Methane is another greenhouse gas that has a large impact and it’s especially important over shorter time periods. Methane is produced mainly by ruminant animals and also it’s released from fossil fuel reserves, such as coal mines and gas fields. Those fires that we see at the top of an oil well for instance, that is the flaring of methane. So methane is actually natural gas too, that we would burn to heat water and so on.
Professor Barry Brook: I’ve done some work recently with a couple of colleagues showing that in fact Australia’s contribution to global warming is more to do with methane, at least in the short term, than it is with anything else. And even more than that, it’s more to do with methane produced by ruminant animals, cattle and sheep and goats for instance.
As part of their natural digestion process they produce methane; they chew the cud, they have a second stomach, and inside that stomach there’s bacteria that break down cellulose in grass to release energy. That’s a process that’s known as an anaerobic process, so it’s in the absence of oxygen and that process causes the release of methane, mostly through belching.
Now because it’s such a powerful greenhouse gas, it has a disproportionate effect on climate change. But most of its impact occurs over a fairly brief period of time, ten or twenty years, almost all the methane is gone. But if you look over that time period and for every ton of methane that’s released, that’s the equivalent to releasing 72 tons of carbon dioxide.
CH4 = 72 * CO2
So it packs a big punch. So to put that into context, Australia’s cattle industry, livestock industry, cattle and sheep, currently releases about 3 million tons thereabouts of methane per year.
Australia’s Live Stock = 3 million tons methane per year. * 72 = 216 million tons methane
Australia’s coal-fired power stations = 180 million tons of CO2
Whereas our coal-fired power stations release about 180 million tons of CO2. So it sounds like coal-fired power stations contribute much more than our cattle do to global warming.
But if you think that methane packs 72 times the punch of CO2 over a 20 year period, then over those next two decades you multiply three by 72. It’s pretty easy to work out that our cattle and sheep industry actually contributes more to global warming than our coal-fired power stations over that period. So that is a vastly underappreciated fact in Australia.
SupremeMasterTV: Do you think that methane is underappreciated in our recent submissions to the government?
Professor Barry Brook: Yes, I think that’s quite apparent. If you look at different greenhouse gases, they have a different contribution to global warming. So you need some method of standardizing them. The basic method that the Intergovernmental Panel on Climate Change (IPCC) uses is to average everything over a 100 year period.
But for methane that is actually a bit pointless, because it’s almost all gone after about 20 years. So you have taken all of its short term contribution and smeared that out over 100 years to make it much less than it would otherwise be. So, if you look at these reports they will suggest it has about 25 times the impact of CO2.
But really when it’s up there in the atmosphere doing its work, it’s 72 times the impact and that makes a big difference. So I think If we want to be serious about our emissions reductions, we have to account for agricultural emissions and we have to, most importantly, account for Australia’s
greatest contribution in the short term too.
SupremeMasterTV: So if we were to have an effect on the animal agriculture, phase it out, would that buy us time with the CO2 technologies?
Professor Barry Brook: Yes, because methane has a very powerful effect, but a short-term effect; ironically, you can do something about it pretty quickly compared to CO2. So although it’s really important right now, it’s something we can really purge out of our emissions very quickly. For reasons disconnected with climate change, for instance, Australia’s sheep population declined from about a 190 million to less than a 100 million since 1992.
That’s had a large impact on Australia’s methane emissions. It gives you an example of how quickly we can make that change, basically halved the emissions produced by Australia’s sheep. There is no reason why you can’t do that for cattle as well. Whereas to change over societies’ infrastructure, for instance from coal-fired power stations to alternative forms of energy, whilst that needs to happen very quickly, it requires a large turnover of capital infrastructure, things which tend to be,
I think, economically more intractable.
Whereas,reducing the head of cattle in Australia is something that could be done quickly, just over a couple of years and have a huge impact on our global-warming impact.
SupremeMasterTV: I’d like to talk to you about the review that you did with Geoff Russell. It’s called, “Meat’s Carbon Hoofprint.” Can you tell us about that?
Professor Barry Brook: Yes, this was a study we did which looked at the relative impact of eating beef on a families’ CO2 emissions compared to some of their other activities that most people might suspect would have a much greater contribution to global warming. The example we used was, let’s say you have a large four-wheel-drive vehicle, a Ford Territory.
So that costs about 17 tons of CO2 emissions to build the thing and then to run it each week it might be about 200 grams of CO2 per kilometer driven. So, you can make the calculation on that basis, it might be 60 kilograms of CO2 a week that you’re using to drive this lumbering Ford Territory around, as well as the emissions that went into producing it.
If you eat what the CSIRO, “Total Wellbeing Diet” recommends is the average weekly consumption of beef, which is somewhere between 3 to 5 kilograms, then you find that when you do the calculations for methane, even when it’s using the standard, which is 25 times as powerful as CO2, and remember earlier I said that really we should be talking about 72 times as powerful. But even at 25 times as powerful, that would be releasing about 200 kilograms a week compared to 60 from your Ford Territory.
So you only need to go for about five years cutting out that meat in your diet and you’ve paid for the emissions of that great four-wheel drive;
that’s one example. Another way to look at it is the amount of emissions produced by a kilogram of steak. That’s so emissions intensive in terms of methane that it’s the equivalent to four times the emissions that would be released by producing a kilogram of aluminum, which is considered incredibly energy intensive, and using a lot of electricity to actually produce that aluminum by electrolysis.
Beef, four times more than producing a kilogram of aluminum, beef being much more of a contributor than driving a four-wheel vehicle. These are facts which are Greatly nderappreciated, so it means you need to be climate conscious about your diet, because there are some impacts in your lifestyle that will have a much greater effect on global warming than others and people don’t actually understand what they are.
SupremeMasterTV: In relation to water that they use to grow beef. There is a lot of, water used in that regard. Can you tell us about that?
Professor Barry Brook:Yes, indeed, there is a lot of water that goes into producing a kilogram of beef and a lot of water also goes into producing dairy products.
Much dairy in Australia is conducted on lands that wouldn’t actually be suitable for dairy except for irrigate agriculture. So this is water that is piped from the Murray and sprayed over vast areas of pasture to produce sufficiently green pastures to produce good milk. But that’s the same water that’s in desperately short supply in Adelaide, that’s killing the Coorong, for instance, because it’s not getting enough water flow.
These are being sprayed onto the green fields of Western Victoria to produce dairy. It’s not actually a very sensible use of water at all.So I think people have to look at the total impact of livestock to really appreciate why they can be particularly damaging to global change. Indeed, looking further afield than Australia, to the tropics, one of the major drivers of tropical deforestation, which in itself is responsible for about 20%, a fifth of all the human CO2 emissions, is driven by clearance of tropical forest for cattle grazing.
So again it’s a driver of deforestation, cause of CO2 emissions directly by chopping down, burning, mostly burning those trees and then once the cattle are there, producing a whole lot more methane as well.
So, there is no doubt that livestock have a long shadow and indeed that was the title of the report produced by the United Nations last year looking at the total impact of livestock on global change. It’s pretty profound and it’s pretty pervasive.
SupremeMasterTV:Do you think that our government should be doing more as regards to letting people know about how they can act as individuals to help with our planetary crisis?
Prof Brook: I think leaving agriculture out of the equation sends the wrong signal because it exempts a sector of society from making greenhouse gas cuts, when in fact every sector of society needs to contribute, so it’s just moving the burden to other parts of society. And it’s not rightfully cknowledging the impact, the environmental impact that rearing animals have on Australia. People often talk about climate change as having a long-term impact and what it’s going to do by the end of the century. Yet we’re observing impacts such as the loss of Arctic summer sea ice, an expansion of tropical weather systems, very intense droughts in sub-Saharan Africa and indeed in Australia.
The sort of impacts we predicted for 20, 30, 50, 100 years off are occurring now.
And there’s also a great risk that we’re going to cross what are known as tipping points in US system, where we start to get runaway climate change, or at least climate change that’s greatly accelerated by changes to the Earth system.
We’re at a crucial social tipping point and a crucial environmental tipping point right now. Now is the time to take action. It’s urgent.
http://suprememastertv.com/tw/bbs/board.php?bo_table=sos_video_tw&wr_id=44&goto_url=&sca=sosv_1&url=link2_0
2008.11.12 SMTV訪談澳洲貝瑞·布魯克教授
主持人：環保的觀眾大家好！
在今天的節目裏澳洲阿得雷德大學的貝瑞·布魯克教授將詳述畜牧業對環境的影響。
布魯克教授是研究全球生態學與保育生物學的專家，他擔任休伯特·威爾金爵士氣候變遷基金會主席，也是阿得雷德大學氣候變遷和永續性研究所的所長。他已出版兩本書和一百多篇科學論文，從不同的觀點探討人類對自然環境和生物多樣性的影響。
他曾獲頒澳洲科學院芬納獎章、新南威爾斯皇家學會埃奇華茲·大衛獎章和南澳皇家學會安德列沃斯獎章。
布魯克教授是名列《宇宙》雜誌的澳洲十大青年科學家。
布魯克教授強調人類必須瞭解甲烷是主要的溫室氣體之一。
布魯克教授：甲烷是很有意思的溫室氣體。許多人可能沒聽過，然而它竟是使人類造成氣候變遷的第二大溫室氣體。大家可能都聽過二氧化碳，而甲烷是影響強大且在短期內就舉足輕重的。另一種溫室氣體甲烷主要來自反芻動物、儲藏石化燃料的煤礦和天然氣田也有。例如，油井上方的火，就是燃燒甲烷所致。因此甲烷其實也是天然氣，我們會用以燒熱水等。
我最近和同事完成的某項研究證明，澳洲的全球暖化貢獻，甲烷其實居功厥偉。至少從眼前來看，其他因素都望塵莫及。而製造甲烷的大功臣則是牛、綿羊和山羊之類的反芻動物。他們在消化過程中會產生甲烷。他們咀嚼反芻的食物，而第二個胃裏的細菌會分解植物的纖維素，釋放其中的能量，該過程即所謂的厭氧程式，在無氧狀態下進行，而所產生的甲烷大多經由打嗝釋放。由於甲烷是一種強效的溫室氣體，對氣候變遷影響甚巨，卻多發生在極短的時間內。甲烷十或二十年即消失殆盡，然而若審視那段時間，會發現釋放一噸甲烷等於釋放七十二噸的二氧化碳，因此威力無窮。
根據這個資料澳洲的養牛業、畜牧業、牛、羊，目前每年約排放三百萬噸甲烷。而火力發電廠約排放一億八千萬噸二氧化碳。電廠的全球暖化貢獻似乎遠多於牛的貢獻。然而若仔細想想，甲烷以二十年為期，效力是二氧化碳的七十二倍，再二十年就變成七十二乘以三倍，很容易算出畜牧業在那段時間對全球暖化的影響更甚於火力發電廠，這是澳洲嚴重忽略的事實。
記者：您認為最近給政府的協議書對甲烷輕描淡寫嗎？
布魯克教授：是的，我認為很明顯。不同的溫室氣體對全球暖化有不同的影響，需用某種方法使它們標準化。跨政府氣候變遷小組所用的基本方法是，以一百年為期，取所有氣體的平均值，然而對甲烷而言，其實有點無意義，因為甲烷經過二十年幾乎就消失了，這種方法取其短期的所有影響均分在一百年間，使它的影響大打折扣。這些報告寫甲烷的影響是二氧化碳的二十五倍，然而當它在大氣中發生作用時，其實是七十二倍，是截然不同的。因此我認為那些報告由於那個會計問題，或因許多人不想面對，而對甲烷一筆帶過。如果要嚴肅看待減少碳排的問題，必須說明農業的碳排最重要的，也要說明目前澳洲最大的碳排元兇。
記者：因此若要影響畜牧業，淘汰它，是否有時間處理二氧化碳？
布魯克教授：是的。因為甲烷效力很強，但影響的時間短。諷刺的是，處理甲烷比處理二氧化碳迅速，因此目前雖迫在眉睫，卻是真正可以迅速清除的碳排，無關氣候變遷的理由。
舉例而言，澳洲的羊自九二年起，約從一億九千萬隻減少至一億隻，對澳洲的甲烷排放量影響甚大，是我們可以快速締造改變的例證。基本上只要澳洲的羊排放的甲烷減半即可。對牛也可如法炮製。
而改變公共建設，例如：以替代能源取代火力發電廠，同時又要迅速進行，勢必需要一大筆建設資金。我認為經濟方面比較棘手。反之，減少澳洲的牛只數量卻可迅速完成，只要數年時間，對遏止全球暖化即可立竿見影。
記者：我想回顧您和傑佛瑞·羅素全寫的《肉類的碳足跡》，您能和我們談談嗎？
布魯克教授：好的，我們這份研究在探討家庭吃牛肉所產生的碳排，並與多數人認為更能影響全球暖化的其他活動作比較，我們所舉的例子是福特四輪傳動的一輛休旅車。製造一輛會排放十七噸二氧化碳，每週駕駛每公里會產生兩百克碳排，以此為計算基準。開這輛笨重的車一周會產生六十公斤碳排，還要加上製造時產生的二氧化碳。如果採取"澳洲聯邦科學與工業研究院"所建議的完全幸福飲食法，每週平均吃三至五公斤牛肉，將會發現，即使是以甲烷的效力為二氧化碳二十五倍的標準計算，記住我剛才提過其實是七十二倍的效力，然而即使是二十五倍，每週的碳排也高達二百公斤，比福特四驅車的六十公斤還高。所以只需五年不吃肉，就可彌補四驅車所產生的碳排。這是一例。
另一項探討是生產一公斤牛排所產生的碳排。大量排放的甲烷等於生產一公斤鋁的四倍排放量。生產鋁的過程需經由電解作用，因此極為耗電。牛肉的碳排量多於生產一公斤鋁的四倍，多於開一輛四驅車所排的碳，這些事實都被嚴重忽略。因此這表示，飲食必須有氣候意識，因為生活方式對全球暖化的影響更甚於其他因素。而人們竟渾然不覺。
記者：關於生產牛肉所耗用的水，生產牛肉消耗許多水，您能談談這點嗎？
布魯克教授：好的，的確。生產一公斤牛肉耗用大量的水，生產乳品亦然。澳洲許多乳品業都設在只適合灌溉農副業的土地上，從莫瑞河引水，遍灑廣闊的牧場，以生產足夠的牧草，生產好牛奶，而這卻正是阿得雷德極度短缺的水，使庫龍因供水不足而奄奄一息。水都用以噴灑維多利亞州西部的綠草地，生產乳製品。這種用水方式一點都不明智，因此人們必須瞭解畜牧業的整體影響，體會它們何以危害全球的變遷。當然，從澳洲看到更遠的熱帶，畜牧業是驅使熱帶砍伐森林的主因之一。砍伐森林本身產生的碳排約占所有人為碳排的二成，只為用來放牧牛只。因此畜牧業又是砍伐森林的元兇，伐木燃燒直接排放二氧化碳，然後在那裏養牛，也產生更多甲烷。因此，畜牧業無疑有著長長的陰影，這正是聯合國去年發表的報告標題，內容關於畜牧業對全球變遷的整體影響，影響相當深遠普遍。
記者：您認為政府應更努力讓人民瞭解，如何盡一己之力助地球度過危機嗎？
布魯克教授：我認為遺漏農業碳排等於發出錯誤信號，因為使社會的這部分不必降低碳排。其實社會的每部分都負有責任，如此只是加重其他部分的負擔，而且不正當地承認畜養動物對澳洲環境所造成的影響。人們經常談論氣候變遷的長期影響和本世紀末的情況，然而我們正目睹北極夏冰的消失；熱帶氣候系統的擴展；非洲撒哈拉和澳洲的極度乾旱；預測二、三十年後，五十、一百年後，才會發生的影響，目前卻正在發生，而且我們即將越過美國系統所謂的臨界點，屆時氣候變遷將如脫韁的野馬，或至少會因地球系統的變化而變本加厲，我們正處於決定性的社會臨界點和環保臨界點，該立即行動了!已經刻不容緩!
Professor Barry Brook on Livestock Agriculture and Climate Change
Professor Brook is an international research leader in global ecology and conservation biology. He holds the Foundation Sir Hubert Wilkins Chair of Climate Change and is Director of the Research Institute for Climate Change and Sustainability at the University of Adelaide.
He has published two books and over 100 scientific papers on various aspects of human impacts on the natural environment and biodiversity. He has been awarded the Australian Academy of Science Fenner Medal, Edgeworth David Medal by the Royal Society of New South Wales, and the H.G. Andrewartha Medal by the Royal Society of South Australia. Professor Brook was listed by Cosmos as one of Australia's top 10 young scientists. Professor Brook emphasizes the need to recognize methane as a major contributor of greenhouse gases.
Professor Barry Brook: Methane is an interesting greenhouse gas; many people may not have heard of it, but it’s actually the second most powerful greenhouse gas in terms of human’s total contribution to climate change.
Everyone has probably heard of CO2. Methane is another greenhouse gas that has a large impact and it’s especially important over shorter time periods. Methane is produced mainly by ruminant animals and also it’s released from fossil fuel reserves, such as coal mines and gas fields. Those fires that we see at the top of an oil well for instance, that is the flaring of methane. So methane is actually natural gas too, that we would burn to heat water and so on.
Professor Barry Brook: I’ve done some work recently with a couple of colleagues showing that in fact Australia’s contribution to global warming is more to do with methane, at least in the short term, than it is with anything else. And even more than that, it’s more to do with methane produced by ruminant animals, cattle and sheep and goats for instance.
As part of their natural digestion process they produce methane; they chew the cud, they have a second stomach, and inside that stomach there’s bacteria that break down cellulose in grass to release energy. That’s a process that’s known as an anaerobic process, so it’s in the absence of oxygen and that process causes the release of methane, mostly through belching.
Now because it’s such a powerful greenhouse gas, it has a disproportionate effect on climate change. But most of its impact occurs over a fairly brief period of time, ten or twenty years, almost all the methane is gone. But if you look over that time period and for every ton of methane that’s released, that’s the equivalent to releasing 72 tons of carbon dioxide.
CH4 = 72 * CO2
So it packs a big punch. So to put that into context, Australia’s cattle industry, livestock industry, cattle and sheep, currently releases about 3 million tons thereabouts of methane per year.
Australia’s Live Stock = 3 million tons methane per year. * 72 = 216 million tons methane
Australia’s coal-fired power stations = 180 million tons of CO2
Whereas our coal-fired power stations release about 180 million tons of CO2. So it sounds like coal-fired power stations contribute much more than our cattle do to global warming.
But if you think that methane packs 72 times the punch of CO2 over a 20 year period, then over those next two decades you multiply three by 72. It’s pretty easy to work out that our cattle and sheep industry actually contributes more to global warming than our coal-fired power stations over that period. So that is a vastly underappreciated fact in Australia.
SupremeMasterTV: Do you think that methane is underappreciated in our recent submissions to the government?
Professor Barry Brook: Yes, I think that’s quite apparent. If you look at different greenhouse gases, they have a different contribution to global warming. So you need some method of standardizing them. The basic method that the Intergovernmental Panel on Climate Change (IPCC) uses is to average everything over a 100 year period.
But for methane that is actually a bit pointless, because it’s almost all gone after about 20 years. So you have taken all of its short term contribution and smeared that out over 100 years to make it much less than it would otherwise be. So, if you look at these reports they will suggest it has about 25 times the impact of CO2.
But really when it’s up there in the atmosphere doing its work, it’s 72 times the impact and that makes a big difference. So I think If we want to be serious about our emissions reductions, we have to account for agricultural emissions and we have to, most importantly, account for Australia’s
greatest contribution in the short term too.
SupremeMasterTV: So if we were to have an effect on the animal agriculture, phase it out, would that buy us time with the CO2 technologies?
Professor Barry Brook: Yes, because methane has a very powerful effect, but a short-term effect; ironically, you can do something about it pretty quickly compared to CO2. So although it’s really important right now, it’s something we can really purge out of our emissions very quickly. For reasons disconnected with climate change, for instance, Australia’s sheep population declined from about a 190 million to less than a 100 million since 1992.
That’s had a large impact on Australia’s methane emissions. It gives you an example of how quickly we can make that change, basically halved the emissions produced by Australia’s sheep. There is no reason why you can’t do that for cattle as well. Whereas to change over societies’ infrastructure, for instance from coal-fired power stations to alternative forms of energy, whilst that needs to happen very quickly, it requires a large turnover of capital infrastructure, things which tend to be,
I think, economically more intractable.
Whereas,reducing the head of cattle in Australia is something that could be done quickly, just over a couple of years and have a huge impact on our global-warming impact.
SupremeMasterTV: I’d like to talk to you about the review that you did with Geoff Russell. It’s called, “Meat’s Carbon Hoofprint.” Can you tell us about that?
Professor Barry Brook: Yes, this was a study we did which looked at the relative impact of eating beef on a families’ CO2 emissions compared to some of their other activities that most people might suspect would have a much greater contribution to global warming. The example we used was, let’s say you have a large four-wheel-drive vehicle, a Ford Territory.
So that costs about 17 tons of CO2 emissions to build the thing and then to run it each week it might be about 200 grams of CO2 per kilometer driven. So, you can make the calculation on that basis, it might be 60 kilograms of CO2 a week that you’re using to drive this lumbering Ford Territory around, as well as the emissions that went into producing it.
If you eat what the CSIRO, “Total Wellbeing Diet” recommends is the average weekly consumption of beef, which is somewhere between 3 to 5 kilograms, then you find that when you do the calculations for methane, even when it’s using the standard, which is 25 times as powerful as CO2, and remember earlier I said that really we should be talking about 72 times as powerful. But even at 25 times as powerful, that would be releasing about 200 kilograms a week compared to 60 from your Ford Territory.
So you only need to go for about five years cutting out that meat in your diet and you’ve paid for the emissions of that great four-wheel drive;
that’s one example. Another way to look at it is the amount of emissions produced by a kilogram of steak. That’s so emissions intensive in terms of methane that it’s the equivalent to four times the emissions that would be released by producing a kilogram of aluminum, which is considered incredibly energy intensive, and using a lot of electricity to actually produce that aluminum by electrolysis.
Beef, four times more than producing a kilogram of aluminum, beef being much more of a contributor than driving a four-wheel vehicle. These are facts which are Greatly nderappreciated, so it means you need to be climate conscious about your diet, because there are some impacts in your lifestyle that will have a much greater effect on global warming than others and people don’t actually understand what they are.
SupremeMasterTV: In relation to water that they use to grow beef. There is a lot of, water used in that regard. Can you tell us about that?
Professor Barry Brook:Yes, indeed, there is a lot of water that goes into producing a kilogram of beef and a lot of water also goes into producing dairy products.
Much dairy in Australia is conducted on lands that wouldn’t actually be suitable for dairy except for irrigate agriculture. So this is water that is piped from the Murray and sprayed over vast areas of pasture to produce sufficiently green pastures to produce good milk. But that’s the same water that’s in desperately short supply in Adelaide, that’s killing the Coorong, for instance, because it’s not getting enough water flow.
These are being sprayed onto the green fields of Western Victoria to produce dairy. It’s not actually a very sensible use of water at all.So I think people have to look at the total impact of livestock to really appreciate why they can be particularly damaging to global change. Indeed, looking further afield than Australia, to the tropics, one of the major drivers of tropical deforestation, which in itself is responsible for about 20%, a fifth of all the human CO2 emissions, is driven by clearance of tropical forest for cattle grazing.
So again it’s a driver of deforestation, cause of CO2 emissions directly by chopping down, burning, mostly burning those trees and then once the cattle are there, producing a whole lot more methane as well.
So, there is no doubt that livestock have a long shadow and indeed that was the title of the report produced by the United Nations last year looking at the total impact of livestock on global change. It’s pretty profound and it’s pretty pervasive.
SupremeMasterTV:Do you think that our government should be doing more as regards to letting people know about how they can act as individuals to help with our planetary crisis?
Prof Brook: I think leaving agriculture out of the equation sends the wrong signal because it exempts a sector of society from making greenhouse gas cuts, when in fact every sector of society needs to contribute, so it’s just moving the burden to other parts of society. And it’s not rightfully cknowledging the impact, the environmental impact that rearing animals have on Australia. People often talk about climate change as having a long-term impact and what it’s going to do by the end of the century. Yet we’re observing impacts such as the loss of Arctic summer sea ice, an expansion of tropical weather systems, very intense droughts in sub-Saharan Africa and indeed in Australia.
The sort of impacts we predicted for 20, 30, 50, 100 years off are occurring now.
And there’s also a great risk that we’re going to cross what are known as tipping points in US system, where we start to get runaway climate change, or at least climate change that’s greatly accelerated by changes to the Earth system.
We’re at a crucial social tipping point and a crucial environmental tipping point right now. Now is the time to take action. It’s urgent.
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