Name: 畜牧業的生命週期評估和溫室氣體排放量 (Life Cycle Assessment and Greenhouse Gas Emissions from Animal Agriculture)
Uploaded: 2021-01-14T06:35:25.000Z
Duration: 20 min 43 s

Scientists agree the major driver behind the rise in global greenhouse gas emissions is

科學家認為主要導致全球溫室效應氣體排放的是

human activity. How does farming fit it and,what is the contribution of animal agriculture

人類活動。農業是如何影響，畜牧業的組成

The consuming public is more and more interested in where their food comes from, what’s the

大眾消費對於他們的食物從何而來越來越有興趣，碳足跡為何

carbon footprint. What’s the carbon footprint, or the what’s

the environmental footprint, of a gallon of milk, or a pound of beef, or a pound of chicken meat?

什麼是環境足跡，一加侖的牛奶，或一磅的牛肉，或一磅的雞肉？

My name is David Schmidt and I’m an agricultural engineer at the University of Minnesota and

我是大衛史密奇，一名明尼蘇達大學的農業工程師和

Regional Coordinator for the national project, Animal Agriculture in a Changing Climate.

研究畜牧業如何改變氣候的國家專案區域協調員

There is a significant amount of miscommunication about the role of agriculture

有很多關於農業對於氣候變遷的錯誤評論

in climate change. Some say that animal agriculture is the largest contributor to greenhouse gas

有些說法畜牧業是產生最多溫室氣體的製造者

emissions while others deny any contribution from animals. The answer lies somewhere in

然而其他人否認動物是製造者來源。這答案在這兩者之中

between. The objective of this video is to provide you with a solid foundation of how

這影片中可以客觀地提供你完整的

emission estimates are calculated and the real contributions of animal agriculture to

排放計算估計和真實的畜牧業排放在

US and global greenhouse gas(GHG) emissions.

Carbon is all around us. It is the fourth most abundant chemical element in the universe,

碳總是圍繞著我們。它是宇宙中第四多的化學成分，

behind hydrogen, helium and oxygen. The biggest reservoir of carbon is stored

排在氫，氦和氧氣之後。存放最多碳的地方在

in rocks- approximately 66,000 gigatons with one gigaton is equal to 1 trillion kilograms.

石頭中-大約660兆噸 ，十億噸等於一兆公斤

The second biggest reservoir is the deep ocean, and the third largest reservoir is in fossil

第二大碳存量是在深海裡，第三大碳存量是在化石中

fuels. The atmosphere and the surface ocean are the smallest carbon reservoirs but possibly

大氣層和海洋表面是碳儲放最少的地方但可能

the most important. Carbon is moving between these reservoirs constantly because of a variety

也是最值得關注的。碳在這儲存區間不斷的移動

of chemical and biological processes. This is known as the carbon cycle.

由於不同的化學及生物反應。這就是大家所了解的碳循環

The total amount of carbon that cycles in and out of the atmosphere naturally each year

大氣層中每年碳循環的總排放量為

is about 210 gigatons. The arrows and yellow numbers indicate this movement, or cycling

2100 億頓。箭頭和黃色的數字代活動變遷，或者是碳循環

of carbon. Plants and oceans are referred to as net carbon “sinks” because they

absorb more carbon from the atmosphere than they emit. These carbon emissions occur in

因為他們從大氣層吸收的碳量大於釋放的量。這些碳排放會發生在

the form of plant respiration and chemical exchanges with the ocean.

植物的光合作用和海洋的化學循環

The red numbers indicate the human influence in the cycle, also known as “anthropogenic

紅色的數字代表人類對碳循環的影響，也被稱之為「人為排放」

emissions.” They can be mostly be attributed to the burning of fossil fuels and changes

常被歸類於燃燒石化燃料及開發土地

in land use. Human activities contribute nine gigatons of carbon emissions annually. About

人類活動的碳排放每年可達90億噸

two gigatons of that carbon gets taken up or absorbed by the ocean. Three gigatons of

大約20億噸的碳可以被使用或被海洋吸收。

that carbon gets absorbed by plants through photosynthesis and taken up in plant soil

30億噸的碳可以被植物吸收做光合作用和植物土壤系統使用

system. All this movement results in an annual net increase of about four gigatons of carbon

這些活動會導致每年淨成長40億噸的碳

As you can see in this diagram, the amount of carbon dioxide in the atmosphere was relatively

你可以看到這些圖表中，大氣層中二氧化碳的量

stable for hundreds of thousands of years, at an average of around 230 parts per million.

在這幾千年間是非常穩定的，約平均百萬分之230

Then about 100 years ago, the CO2 concentration in the atmosphere began climbing to where

大約100年前，大氣層中二氧化碳的濃度攀升到現在的水位

it is right now, about 400 parts per million.

This animated diagram more dramatically illustrates the rise in carbon dioxide levels in the earth’s

這個動態圖表更戲劇化的展現二氧化碳在大氣層中

atmosphere in more recent years, since 1979. The numbers on the left and right indicate

自1979年上升的程度。左側及右側的數字代表

the CO2 concentration in parts per million. Again this indicates the current CO2 level

二氧化碳濃度比例   以百萬分為單位。再次說明現在二氧化碳的濃度

reaching up to and even beyond 400 parts per million.

已經觸及或甚至超越百萬分之400

While we do not intend to focus on all of the greenhouse gases in this lesson, it is

我們並沒有要聚焦所有溫室氣體，

important to note that carbon dioxide is not the only greenhouse gas. The most common greenhouse

重點是了解到二氧化碳並不是唯一的溫室氣體。最常見的溫室氣體

gas is water vapor, followed by carbon dioxide , methane , nitrous oxide and fluorinated

是水蒸氣，緊接在二氧化碳之後，甲烷，一氧化二氮和氟化氣體

gases. Excluding water vapor, the combined sources of carbon dioxide, primarily from

除了水蒸氣，二氧化碳的組成來源主要是從

fossil fuel use and land use change, make up about 77% of the global greenhouse gases.

化石燃料及土地開發，產生約77%的全球溫室氣體

Because these other gases trap different amounts of energy per molecule of gas, scientists

因為這些氣體是由不同的能量分子組成，

have normalized the data into something called Carbon Dioxide Equivalents, or CO2 equivalents.

科學家把這些數據標準化為二氧化碳當量 (CO2e)

This “equivalent” refers to the equivalent heating potential of the gas. This is also

「當量」是以潛在熱能氣體的比例為依據

known as radiative forcing or global warming potential. For instance, a single molecule

這也被稱之為輻射強迫或全球暖化潛勢。舉例來說，

of methane will trap approximately 25 times the amount of energy as will a single molecule

一個分子的甲烷大約等於一分子的二氧化碳的25倍

of carbon dioxide. So methane has a CO2 equivalent of 25. Nitrous Oxide has a CO2 equivalent

所以甲烷的二氧化碳當量是25。氧化亞氮的二氧化碳當量是298

of 298. This use of CO2 equivalents allows us to evaluate the impact of the gases on

使用二氧化碳當量可以讓我們去估計氣體影響環境的程度

the environment - not just the amount of these gasses in the atmosphere.

不只是衡量大氣層中氣體的含量

Anthropogenic greenhouse gases are emitted by many sources and from every country. Together

人為的溫室氣體是來自每個國家不同的排放來源

these nations contribute a world total of 45 thousand million metric tons of CO2 Equivalents.

這些國家一共產生4.5億噸二氧化碳當量

This graph shows percentages of greenhouse gas emissions by country in 2012. The United

這圖表為2012各國家溫室氣體排放的百分比

States is currently the second highest emitter of these gases, contributing about 15% of

美國為現在第二高排放量的國家，大約占全世界排放的15%

the world total. The highest emitting country is China. However, this same information can

最大的排放量國為中國。然而，相同的資訊

be evaluated based on emissions per capita. This breakdown shows the US at about 19 tons

可以用人均排放量進行評估。結果顯示美國每年每人約19噸二氧化碳當量

CO2e per year per person vs China at 7.5 tons CO2e per year per person.

而中國每年每人約7.5噸二氧化碳當量

Taking a closer look at the sources of greenhouse gas emissions in the United States alone by

更近一點觀察美國經濟部分的溫室氣體排放

economic sector, we see that agriculture contributes 9 percent of total emissions in

the US. Total emissions in the US add up to approximately 6,673 million metric tons of

美國總排放量加起來大約667.3萬噸

CO2 Equivalents. Agriculture’s 9% represents about 515 Million Metric Tons of that amount.

二氧化碳當量。農業的9%大約代表51.5萬噸

Looking at the agricultural sector itself, we can see that agricultural soil management

單看農業部份，我們看到農業土壤管理

is the biggest source, it accounts for about 50% of total agricultural emissions. This

是最大的主因，大約占50%的總農業排放

is followed by enteric fermentation at about 32% and manure management at 15%.

再來是腸道發酵32%和糞便管理15%

Now looking at the type of gases emitted, about 55% of the agricultural emissions are

現在來看看排放型態，大約55%的農業排放是從

from nitrous oxide, which is produced naturally through the the microbial process of nitrification

一氧化氮，其通過土壤中礦物氮的硝化

and denitrification of mineral nitrogen in the soil. The remaining 45% is from enteric

和反硝化的微生物過程自然產生。剩餘45%是從

methane or from methane formed during the microbial breakdown of manure. Note that these

腸道發酵或在糞便微生物分解期間形成的甲烷。

emissions are only the direct emissions of greenhouse gases occurring on the farm. Other

這排放是在農場上直接排放溫室氣體

emissions that would occur off farm - like emissions from fertilizer production or electricity

其他不是在農場上排放的 - 像施肥的排放或是電力使用

used on the farm are not included in these numbers.

We can also look more closely at emissions by animal species. In this chart you can

我們也可以深入研究動物的排放量。在這張圖中

see the comparisons between beef cattle, dairy cattle, swine, poultry and all other livestock.

你可以看到肉牛、乳牛、豬、家禽和其他家禽類的比較

These differences are primarily a function of total animal numbers and the contribution

這些差異主要是不同的動物數量和

of enteric fermentation. Again these are direct emissions for animal production and do not

腸道發酵的程度。而這些動物產品的直接排放並沒有

include emissions from the production of things like animal feed.

Overall if you look at all animals in the united states for example – the beef sector

總體來說如果拿美國的動物來舉例-牛肉

would have the greatest impact on carbon footprint of this nation but that’s only because there

對美國影響碳足跡最大的唯一原因是

are so much more beef animals than dairy animals. We have 90 million beef animals and 9 million

有太多的肉牛相較於乳牛。我們有9000萬頭的肉牛與900萬頭的

dairy animals, so 10 times more beef animals.

However, a better way to think about greenhouse gas emissions is in terms of emissions per

然而，一種更好的方式去思考溫室氣體排放是根據

unit of production. We can look at kilograms of CO2 equivalents per kilogram of product

每單位生產的排放量。我們可以用每公斤為單位的二氧化碳當量

produced or product consumed. This evaluation includes not only direct emissions from the

的製成或產品消耗為單位。這估計方式不只包含農場直接排放

farm, but also the emissions that occur after the products leave the farm. We will discuss

this further a little later in the video.This graph compares the greenhouse gas emissions

我們會晚點會再進行討論。這圖表比較了幾種產品以公斤為單位

of several products on per kilogram basis. Of all the products, lamb is the highest emitter

的溫室氣體排放。在所有產品中，羊是每公斤排放量最高的

per kilogram of product consumed, and beef is the second highest emitter at 27 kilograms

產品，而牛肉是第二高排放量的產品為27公斤

of CO2 equivalents per kilogram of beef consumed. Dairy is much lower in emissions, with 1.9

二氧化碳當量。乳製品是排放量最少的

kilograms of CO2 equivalents per kilogram of milk consumed.

Before getting further into attributing emissions to different sectors of animal agriculture

再進一步將不同種類的排放歸於畜牧業

or to different sources on the farm, we’ll look at the system used to measure and calculate

或不同的農場來源前，我們來看看用來測量和計算排放的系統

these emissions. There is a way to quantify greenhouse gases.

有一種可以來量化溫室氣體的方式

This quantification method is called LCA, life cycle assessment. It has been done for

這個測量方法稱之為生命周期評估(LCA)

many years and it has been done by many different groups using different methodologies.

這已行之有年而且被許多的團體用不同的測量方法實驗

The Life Cycle Assessment, or LCA, is an accounting method that tracks all of the greenhouse gas

生命週期評估(LCA)，是一種會計準則去記錄溫室氣體

emissions produced by a given process, product or system. Often this is called a ‘cradle

從生產過程、產品或系統化的排放程度。亦被稱之為