Apr 19, 2018 | Updated: 09:54 AM EDT

How to Make Biofuel: Feeding Algae with Wastewater

Apr 04, 2015 11:41 AM EDT

As society shifts to wanting more sustainable sources fuels and other products, many groups are looking at different organisms to act as biological factories. Although it's likely that each type of organism will have its place, one of the best options for many applications seems to be algae. Algae, like plants, produce their energy through photosynthesis; at the same time they tend to grow more quickly because they are single celled. With the fact that they can even grow in saltwater depending on the species, it seems like a silver bullet for many biochemical issues.

However, like plants they also need trace nutrients like nitrogen and phosphorus. Large-scale farming of algae would produce direct competition for chemical fertilizers that we use for food. While plenty of research is investigating biofuels from algae, most industrial farming has shifted toward low volume/high-value products, like pharmaceuticals. But that may change thanks to a recent experiment done by researchers from Rice University. (via EurekaAlert)

Despite concerns that large-scale algae growth will use up too much nitrogen and phosphorus, we actually have a source it that we don't know what to do with. After sewage is treated to to remove any solids, it's still filled with dissolved contaminants. This includes a good amount of nitrates and phosphorus, and despite them being plant nutrients, just dumping them into the environment can have damaging side effects.

So the somewhat obvious solution is to grow algae in this wastewater. Plans for something like this and small-scale experiments have been done, but before this experiment by Rice University, only one large-scale experiment had been done. Even after this, there are still many questions to be answered, but the results are encouraging.

The scientists worked with a sewage treatment plant in Houston and set up 12 open containers of wastewater, 600 gallons each. Each container had a different set of algae. Some were algae monocultures, containing only one strain. Others were combinations of different species, and some even contained small fish that eat algae predators. Despite these different conditions, all containers showed tremendous algae growth. This is good news, because while a mix of species is generally more stable, algae monoculture would be more efficient and productive for producing biofuels.

It also removed 90% of nitrates and 50% of phosphorus from the water. Meaning that using wastewater as feedstock for algae could also solve the issue of nutrient contamination. By killing two birds with one stone it's likely that more research of this nature will take place. Including more large-scale studies that examine different environmental factors, such as temperature and different starting concentrations of the nutrients. However, it looks hopeful that this may be a solution to our biofuel needs. 

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