Shifting from freshwater to seawater-based biofuels production could potentially save clean water for human consumption.
The production of biofuels (1st generation) requires edible feedstock (corn, soy, etc) and water in the process. In order to get enough amount of feedstock, huge amount of farmland is occupied and water is used to irrigate the crops. Moreover, the production of biofuels also needs a significant amount of freshwater. By estimation, for every 50 million gallons of bioethanol production, about 150-200 million gallons of freshwater is required. With the current world population of 7.9 billion and is projected to increase in future, the expansion of biofuels production could potentially create water crisis between human consumption versus biofuels production.
Lignocellulosic biofuels (2nd generation) refer to fuels derived from lignocellulosic biomass as feedstock. These biomasses include wheat straw, rice straw, sugarcane bagasse and oil palm empty fruit bunches. The advantages of using them as feedstock for biofuels production are these materials are non-edible and cheap agricultural wastes. In general, there are four key steps in lignocellulosic biofuels production, which are (i) pre-treatment of feedstock, (ii) saccharification, (iii) fermentation of sugars derived from lignocellulosic biomass for biofuels production, and (iv) product recovery. Researchers initially hope that lignocellulosic biofuels would require less water. However, the same drawback is arising that a huge amount of freshwater is consumed in the bioprocessing of lignocellulosic biomass.
To address the issue of requiring large amount of freshwater to produce biofuels, researchers are exploring the possibility of using seawater for biomass processing and for fermentations. Research reported by Zaky and colleagues in journal Scientific Reports (Article title: The establishment of a marine focused biorefinery for bioethanol production using seawater and a novel marine yeast strain) showed marine yeast Saccharomyces cerevisiae AZ65 could produce bioethanol in seawater-based media with comparable production efficiency to freshwater-based bioethanol production.
Under the Newton Fund program awarded to CNAP, University of York (UK) and Faculty of Science, Universiti Teknologi Malaysia led by Professor Neil Bruce and Dr. Chong Chun Shiong, the collaborative research on using seawater for oil palm empty fruit bunches (EFBs) processing found that microorganisms from mangrove environments could decompose EFBs. Specifically, Meridianimaribacter sp. strain CL38 obtained from mangrove soil demonstrated its ability to digest EFBs in seawater-based media via the actions of lignocellulose degrading enzymes. Fermentable sugars are produced from the process. These sugars could be used to produce biofuels. Moreover, research on development of fermentation systems using seawater media by Newton Fund sub-group leaders (Assoc Prof. Dr Madihah Md Salleh and Dr Adibah Yahya) found that Clostridium beijerinckii was able to produce bioethanol and biobutanol in 100% of seawater-based media (without using freshwater). The findings suggest seawater could substitute freshwater to produce biofuels.
While this research is still at the early stage, it is a fascinating niche area with great potential to solve water shortage issue. Research in the lab scale alone will not ensure the success of seawater-based biofuels. Development of this area will need collaboration and coordination from different experts formed under Energy – Food – Water – Environment Nexus, accompanied by funding from governments/investors and with new policies that aid the expansion of seawater-based biofuels production.
Article published in FS Research Hub (November 2021)
By Dr Chong Chun Shiong (Environmental Biotechnology Research Group)