可再生能源真的能取代化石燃料嗎?

可再生能源真的能取代化石燃料嗎?

As global temperatures and energy demand rise simultaneously, the search for sustainable fuel sources is more urgent than ever. But how can renewable energy possibly scale up to replace the vast quantities of oil and gas we consume?

隨著全球氣溫和能源需求的同時(shí)上升，尋找可持續(xù)的燃料來(lái)源比以往任何時(shí)候都更加緊迫。但是，可再生能源如何能夠大到可以取代我們消耗的大量石油和天然氣呢?

Plant power is a significant piece of the answer, says Purdue scientist Maureen McCann.

普渡大學(xué)的科學(xué)家莫林·麥肯說(shuō)，植物能源是個(gè)不錯(cuò)的答案。

“Plants are the basis of the future bioeconomy,” she says. “In my mind, building a sustainable economy means we stop digging carbon out of ground and begin to make use of one and a half billion tons of biomass available in the U.S. on an annual basis. That's the strategic carbon reserve that we need to exploit in order to displace oil.”

“植物是未來(lái)生物經(jīng)濟(jì)的基礎(chǔ)，”她說(shuō)。“在我看來(lái)，建設(shè)可持續(xù)經(jīng)濟(jì)意味著我們停止從地下挖掘碳，并開(kāi)始利用美國(guó)每年15億噸的生物質(zhì)。這就是我們?yōu)榱巳〈投枰_(kāi)發(fā)的戰(zhàn)略碳儲(chǔ)備。”

McCann is a professor of biological sciences, former director of the Energy Center at Purdue’s Discovery Park, and president-elect of the American Society of Plant Biologists. She has spent her academic career looking at plant cell walls, which contain some of the most complicated molecules in nature. By studying a wide range of plants — from poplar trees to zinnias — ­her lab has characterized hundreds of plant genes and their products in an effort to understand how they all interact and how they could be manipulated in advantageous ways.

麥肯是生物科學(xué)教授，普渡大學(xué)發(fā)現(xiàn)公園能源中心前主任，美國(guó)植物生物學(xué)家學(xué)會(huì)當(dāng)選主席。她在學(xué)術(shù)生涯中一直在研究植物細(xì)胞壁，其中包含自然界中一些最復(fù)雜的分子。通過(guò)研究從楊樹(shù)到百日菊等一系列植物，她的實(shí)驗(yàn)室對(duì)數(shù)百種植物基因及其產(chǎn)物進(jìn)行了表征，試圖了解它們是如何相互作用的，以及如何以有利的方式操縱它們。

The ethanol industry uses enzymes to break starchy corn kernels down into glucose molecules, which, in turn, are fermented by microorganisms to produce usable fuel. Many researchers have been working on the possibility of getting more glucose by breaking down cellulose — the primary fibrous component of all plant cell walls — which is much more abundant than starch. However, McCann says their methods might be ignoring a valuable resource.

乙醇工業(yè)利用酶把淀粉玉米粒分解成葡萄糖分子，葡萄糖分子又被微生物發(fā)酵產(chǎn)生可用的燃料。許多研究人員一直在研究通過(guò)分解纖維素(所有植物細(xì)胞壁的主要纖維成分)獲得更多葡萄糖的可能性，纖維素比淀粉豐富得多。然而，麥肯說(shuō)他們的方法可能忽略了一個(gè)有價(jià)值的資源。

In addition to cellulose, cell walls contain many complex, poly-aromatic molecules called lignins. These compounds can get in the way of enzymes and catalysts that are trying to access cellulose and break it down into useful glucose. As a result, many labs have previously attempted to create plants that have more cellulose and fewer lignins in their cell walls.

除了纖維素，細(xì)胞壁還含有許多復(fù)雜的多環(huán)芳烴分子，稱(chēng)為木質(zhì)素。這些化合物會(huì)阻礙酶和催化劑的作用，這些酶和催化劑試圖獲取纖維素并將其分解成有用的葡萄糖。因此，許多實(shí)驗(yàn)室先前曾試圖創(chuàng)造出在細(xì)胞壁中含有更多纖維素和更少木質(zhì)素的植物。

But it turns out lignins are important for plant development and can be a valuable source of chemicals. As director of Purdue’s Center for Direct Catalytic Conversion of Biomass to Biofuels (C3Bio), McCann collaborated with chemists and chemical engineers in maximizing utilization of available biomass, including lignins. A nine-year grant from the U.S. Department of Energy funded C3Bio researchers’ work toward using chemical catalysts to transform both cellulose and lignins into liquid hydrocarbons, which are more energy-dense than ethanol and fully compatible with engines and existing fuel infrastructure.

但事實(shí)證明，木質(zhì)素對(duì)植物的生長(zhǎng)非常重要，是一種很有價(jià)值的化學(xué)物質(zhì)。作為普渡大學(xué)生物質(zhì)能直接催化轉(zhuǎn)化生物燃料中心(C3Bio)的主任，麥肯與化學(xué)家和化學(xué)工程師合作，最大限度地利用現(xiàn)有生物質(zhì)能，包括木質(zhì)素。C3Bio的研究人員使用化學(xué)催化劑將纖維素和木質(zhì)素轉(zhuǎn)化為液態(tài)碳?xì)浠衔铮@種化合物的能量密度比乙醇高，與發(fā)動(dòng)機(jī)和現(xiàn)有的燃料基礎(chǔ)設(shè)施完全兼容。

In light of lignins’ usefulness, McCann and her colleagues are interested in alternative biofuel optimization strategies that don’t involve reducing plants’ lignin content. For example, if the researchers can modulate the strength of the “glue” between plant cells, they can make it easier for enzymes to access cellulose and also reduce the amount of energy needed for shredding the plant material. Another approach involves genetically engineering living, growing plants to incorporate chemical catalysts into their own cell walls, which will help eventual breakdown be faster and more complete.

鑒于木質(zhì)素的實(shí)用性，麥肯和她的同事對(duì)不涉及減少植物木質(zhì)素含量的生物燃料優(yōu)化策略很感興趣。例如，如果研究人員能夠調(diào)節(jié)植物細(xì)胞間“膠水”的強(qiáng)度，他們就能讓酶更容易地接觸到纖維素，同時(shí)還能減少粉碎植物材料所需的能量。另一種方法是通過(guò)基因工程改造活的、生長(zhǎng)的植物，將化學(xué)催化劑融入它們自己的細(xì)胞壁，這將有助于最終更快更徹底地分解。

“In both cases, this work is a reflection of synthetic biology thinking,” McCann says. “We don't simply take what nature gives us; we think of ways to improve the performance of the biomass using the entirety of the genetics toolkit.”

“在這兩種情況下，這項(xiàng)工作都反映了合成生物學(xué)的思考，”麥肯說(shuō)。“我們不是簡(jiǎn)單地接受自然賦予我們的東西;我們是想辦法利用整個(gè)基因?qū)W工具箱來(lái)提高生物質(zhì)的性能。”