? ? ? ? 藻類生物燃料遇到點煩心事。這種替代燃料能源，和許多生物燃料一樣，有助于減少碳排放，而且還不占用糧食生產(chǎn)用地。但是它卻被殼牌和埃克森美孚這樣的大公司給拋棄了，這些公司正在放棄對這個環(huán)境友好燃料的投資。為什么這么有前途的技術沒有能夠開花結果，我們還能做什么來挽回它呢?
? ? ? ? ?藻類是生長在水中，從二氧化碳和陽光中產(chǎn)生能量的光合生物。單細胞微藻類富含脂肪，可以用來轉化成生物柴油，這是最常見的生物燃料。生產(chǎn)生物燃料的原材料有很多種，包括玉米和烹調過的食用油。但是藻類很特別，因為它們生產(chǎn)迅速，能夠產(chǎn)生大量的燃料(高生產(chǎn)率)。
在過去的十年中，能源行業(yè)已經(jīng)投入大量的資金用于藻類生物燃料生產(chǎn)的發(fā)展。這是非常有意義的，因為，十年前，由于高油價以及人們對碳排放造成氣候變化意識在增強，有必要尋找化石燃料的替代品。藻類生物燃料被吹捧為解決這些問題的答案，從而導致了大量投資的跟進。
不幸的是，我們對整個事情缺乏完整的規(guī)劃。生產(chǎn)藻類生物燃料的企業(yè)難以在更大的規(guī)模保持其高生產(chǎn)力，而且他們發(fā)現(xiàn)肉食動物經(jīng)常污染他們的農(nóng)場。他們還發(fā)現(xiàn)，這種生產(chǎn)方式并不經(jīng)濟。建造池塘種植藻類以及為它們提供足夠的陽光和養(yǎng)分用于生長，代價高昂，雪上加霜的是，石油價格暴跌。
不只是生物燃料
藻類不僅僅能夠生產(chǎn)生物燃料。實際上，藻類類似于一個微型工廠，可以生產(chǎn)各種有用的化合物，這些物質可以用來制造一系列不同種類的產(chǎn)品。
例如，藻類能產(chǎn)生大量的ω-3脂肪酸，這是一種重要的膳食補充劑。這意味著它可能是一個可持續(xù)的ω-3的植物來源，否則我們只能通過吃魚或倒胃口的鱈魚魚肝油來獲取ω-3脂肪酸。更普遍的是，藻類是維生素、礦物質和蛋白質的良好來源，人們經(jīng)常服用如小球藻、螺旋藻等，因為它們對健康有益。
另一個用途是藻類可以制成生物塑料。普通塑料是一種由化石燃料制成的產(chǎn)品，而且很難降解，不環(huán)保。藻類能夠以較低的碳排放，甚至在某種程度上能夠吸收碳排放的方法來生產(chǎn)生物塑料。藻類的利用有助于防止塑料在環(huán)境中的積累。
產(chǎn)品的多樣性可能是最后開發(fā)藻類生物燃料的關鍵。這些產(chǎn)品中有很多高價值的化學品，銷售價格遠遠高于生物燃料。因此通過將藻類與生物柴油生產(chǎn)結合，我們可以補貼燃料價格，從而抵消藻類養(yǎng)殖成本高的問題。
這個概念，被稱為“生物煉制”，是新一輪的藻類研究，希望能夠解決過去十年存在的問題。我們知道煉油廠生產(chǎn)塑料、纖維和潤滑油以及燃料?，F(xiàn)在我們希望以完全相同的方式開發(fā)藻類生物煉制。
藻類生物煉制
為了使這個方法更具成本效益和可持續(xù)性，我們需要利用廢熱、二氧化碳和營養(yǎng)物質供藻類生長。這些物質從發(fā)電廠、工廠和水處理廠都很容易獲取，這就能夠降低一部分藻類生長的成本。藻類燃料生產(chǎn)后，會殘留下大量的蛋白質碳水化合物和其它分子。這些物質都可以轉化成上文提到的各種產(chǎn)品，或者可以用于生產(chǎn)沼氣(另一種燃料來源)。這些沼氣可以出售，或者用它們在生物煉制廠中生產(chǎn)藻類所需要的熱量，這個閉合回路使整個生產(chǎn)過程更加高效。
我們很容易就可以了解到，這個過程提出了一個可持續(xù)的、有利可圖的用藻類生產(chǎn)生物燃料的方式。事實上，已經(jīng)有公司將這一概念應用到具體工作中。在2014年，藍寶石能源公司，世界上最大的藻類生物技術公司之一，宣布他們正在擴大業(yè)務范圍，包括營養(yǎng)補充劑以及生物燃料。業(yè)務重點向生物煉制方向轉移對許多想要豐富產(chǎn)品線的公司來說，已經(jīng)越來越普遍。
顯然，藻類生物煉制還不能解決藻類商業(yè)化今天所面對的所有問題。這個行業(yè)還面臨許多關鍵問題，藻類大規(guī)模生產(chǎn)的效率損失問題，以及藻類培養(yǎng)過程中的污染問題。這些問題只能通過持續(xù)的努力研究來解決。生物煉制很可能是人類未來擺脫化石燃料的下一步計劃。
英文原文：
Opinion: Can we save the algae biofuel industry?
Algal biofuels are in trouble. This alternative fuel source could help reduce overall carbon emissions without taking land from food production, like many crop-based biofuels do. But several major companies including Shell and ExxonMobil are seemingly abandoning their investments in this environmentally friendly fuel. So why has this promising technology failed to deliver, and what could be done to save it?
Algae are photosynthetic organisms related to plants that grow in water and produce energy from carbon dioxide and sunlight. Single-celled microalgae can be used to produce large amounts of fat, which can be converted into biodiesel, the most common form of biofuel. There are many possible ingredients for making biofuels, from corn to used cooking oil. But algae are particularly interesting because they can be grown rapidly and produce large amounts of fuel relative to the resources used to grow them (high productivity).
In the last decade or so, vast amounts of money have been invested in the development of algae for biofuel production. This made sense because, ten years ago, there was a need to find alternatives to fossil fuels due to the high oil price and the increasing recognition that carbon emissions were causing climate change. Algal biofuels were touted as the answer to these twin problems, and huge investment followed.
Unfortunately, things didn’t go quite to plan. Companies making algal biofuels struggled to retain their high productivity at a larger scale and found predators often contaminated their farms. They also found that the economics just didn’t make sense. Building the ponds in which to grow the algae and providing enough light and nutrients for them to grow proved too expensive, and to make matters worse the oil price has plummeted.
Beyond biofuels
But algae don’t just produce biofuels. In fact, algae are like microscopic factories producing all sorts of useful compounds that can be used to make an amazingly diverse range of products.
For example, algae can produce large amounts of omega-3 fatty acids, an important dietary supplement. This means it could be a sustainable, vegetarian source of omega-3, which is otherwise only available from eating fish or unappetising cod liver tablets. More generally, algae are excellent sources of vitamins, minerals and proteins, with species such as Chlorella and Spirulina commonly being consumed for their health benefits.
Another useful product that can be made from algae is bioplastic. Regular plastic is a product of fossil fuels and takes an extremely long time to break down, which makes it very environmentally unfriendly. Bioplastic from algaecan be produced with low carbon emissions, or even in a way that absorbs emissions. Their use could help prevent the build up of plastic in the environment.
The diversity of these products may be the key to finally developing algal biofuels. Many are high-value chemicals, selling for a much higher price than biofuels. So by combining them with biodiesel production, we could subsidise the price of the fuel and offset the high costs of algal cultivation.
This concept, known as a “biorefinery”, is part of a new wave of algae research that aims to overcome the issues of the past decade or so. We already know that oil refineries produce plastics, fibres and lubricants as well as fuels. Now we are hoping to develop algal biorefineries in exactly the same way.
Producing an algal biorefinery
To make this model cost-effective and sustainable, we would need to use waste sources of heat, carbon dioxide and nutrients to grow the algae. These are widely available from power plants, factories and water treatment plants and so could reduce some of the costs of growing algae. After making algal fuel, you’re left with lots of proteins, carbohydrates and other molecules. These can be converted into the kinds of products mentioned above, or used to produce biogas (another fuel source). This biogas can be sold or used at the biorefinery to produce heat for the algae, closing the loop and making the whole process more efficient.
It’s easy to see how this process could be a way forward for sustainable, profitable biofuel from algae. In fact, there are companies already applying this concept to their work. In 2014 Sapphire Energy, one of the world’s largest algal biotechnology companies, announced that they were diversifying their work to include nutritional supplements as well as biofuels. This move towards biorefinery is becoming more common and many firms diversifying their product lines.
Clearly, the algal biorefinery will not solve all the problems facing commercial algal cultivation today. There are still key issues facing the loss of yield at very large scales, and the contamination of algal cultures by predators that eat your crop of algae. These issues will only be solved by continued research efforts. However, biorefinery may well be the next step towards a future free from fossil fuels.