Biofuels From Algae In Wastewater


Algae could be used to both treat wastewater and generate fossil fuels, according to two recently published studies. 

Indian scientists working on producing biofuel from algae cultured in municipal wastewater say they are enthused by the findings of a recent study conducted at the biotechnology department of Rice University, Houston.

The findings of the Rice University team, published in March in Algae, show that strains of oil-rich algae were capable of removing more than 90 percent of nitrates and more than 50 percent of phosphorus from wastewater.

A similar study done by Indian Institute of Technology (IIT), Kharagpur in 2010 on algae grown in municipal wastewater had achieved similar results. Meenakshi Banerjee Bhattacharjee, India-born co-author of the Houston study, tells SciDev.Net that the method can be readily replicated. “It would work very well in a country like India where the climate is suitable for algal growth and where there are many indigenous strains.”

Algal culture, which is in its early stages, has so far relied on heavy investment in land and water making algae cultivation for biofuels unsustainable. But these studies have found that using wastewater at a treatment facility proves a win-win situation by providing a nutrient-rich base for growing while cleaning wastewater of pollutants. Bhattacharjee however cautions that the method may not be suitable for systems in which water was flowing, such as polluted drains and rivers. “For this to work you have to have stagnant waters (or wastewater contained within an area) such as in a wastewater treatment system or a sewage processing plant.” To make this system economical and sustainable, oil-rich species of algae are used to treat wastewater by reducing nitrate and phosphate content, which are the main causes of eutrophication (oversupply of nutrients inducing explosive growth of plants and algae in water bodies).

The Houston scientists showed that it was possible to maintain a single strain of algae (monocultures) in tanks, unlike in open ponds where there usually is contamination with other algae strains. “If monocultures can be maintained that opens up avenues for obtaining special products—this cannot be done if the water becomes contaminated with other strains,” Bhattacharjee explains.

The IIT-Kharagpur study had also examined biodiesel production with algae in multiple settings including at a municipal waste treatment plant which showed high biodiesel production. Nirupama Mallick, author of the 2010 study and professor at the department of agriculture and food engineering at IIT-Kharagpur, says that suitable indigenous algae strains are available in India.

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Prasad Yerra
While research and development of algal biofuels are currently receiving much interest and funding, they are still not commercially viable at today’s fossil fuel prices. However, a niche opportunity may exist where algae are grown as a by-product of high rate algal ponds (HRAPs) operated for wastewater treatment. In addition to significantly better economics, algal biofuel production from wastewater treatment HRAPs has a much smaller environmental footprint compared to commercial algal production HRAPs which consume freshwater and fertilisers.
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