Biohydrogen Production from Potato Waste Using Dark Fermentation
Authors:   , Shahab Nimra 
Published: November 2023

The excessive use of fossil fuels as the primary energy source has resulted in significant environmental and economic challenges, including greenhouse gas emissions and the depletion of finite fossil fuel resources. To address these issues, there is a growing need for alternative and sustainable energy sources. Hydrogen holds promise as a clean and renewable energy option, and biohydrogen, produced through biological water splitting using microorganisms, emerges as a potential solution. Shifting towards biohydrogen production can help reduce greenhouse gas emissions, promote energy security, and lessen dependence on finite fossil fuels, making it a crucial step towards a more sustainable energy future. The assessment of biohydrogen production was performed in the study using obligative facultative anaerobe Clostridium butyricum (NCTC 7423) in the batch experiments. The initial experiment tested the potential of the strain to produce hydrogen from pure carbohydrate sources glucose and starch. Under the inoculum to substrate ratio of 9%, the strain showed the yield of 1.23 mol H2 / mol glucose and 0.73 mol H2 / mol glucose from glucose and starch with the substrate degradation efficiency of 70% and 60% in glucose and starch. The theoretical yield of hydrogen from carbohydrate is 2 moles for butyrate pathway and 4 moles for acetate pathway and their respective efficiencies are 16.75% and 33.51%. The efficiency of the strain from the conducted experiments using glucose and starch were 60% and 36%. The effect of temperature was further tested for the provided strain which resulted in the improved substrate degradation efficiency from 70% to 90% but the hydrogen production reduced at higher temperature. The strain has been reported to utilise starch as a substrate, this study further tested the use of natural waste rich in carbohydrate which in this case was potato waste. The potato waste was able to produce hydrogen with accompanied pre-treatment method which helps to improve the hydrolysis of carbohydrate present in the biomass. The potato was thermally and mechanically treated for biohydrogen production, three types of potato wastes were tested and the higher biohydrogen production was achieved in the boiled potato waste compared to raw and dried potato waste. The yield of the raw, dry and boiled potato waste achieved in the study are 65.05 ml/ g VS, 30.58 ml/ g VS, 103.39 ml/ g VS. The possibility of hydrogen production from all types of waste showed that potato in any form can be used to produce biohydrogen. The biohydrogen energy obtained by treating three types of potato waste are 9.3 kJ, 3.5 kJ, and 12.9 kJ from raw, dry and boil potato. The COD reduction obtained in the three types of waste were 17%, 11% and 23 %. The possibility of biohydrogen production from potato is a step towards making this process viable and energy efficient. Biohydrogen production is affected by the process parameters, therefore response surface analysis was used to optimise the process parameter pH and temperature for biohydrogen production. The analysis showed that pH and temperature are significant factors for biohydrogen production and the optimum pH and temperature was found to be 4.5 and 39oC which resulted in 129.50 ml H2/g VS . The analysis of volatile fatty acid in the experiments also showed that the strain utilised butyrate pathway for biohydrogen production as the butyric acid production was dominant in all the experiments. By maintaining the pH and temperature the COD reduction further increase to 29% which shows that both pre-treatment and maintained process parameter can helps to improve the hydrogen yield. Biohydrogen offers a promising alternative to fossil fuels, and Clostridium butyricum shows potential for hydrogen production from various carbohydrate sources, including potato waste. By optimizing process parameters, such as pH and temperature, biohydrogen production efficiency can be significantly improved. The findings highlight the versatility and renewable potential of potato waste for biohydrogen production, contributing to the development of sustainable energy solutions and addressing environmental concerns associated with traditional fossil fuel usage. Further research and investment in biohydrogen technology are essential for achieving a sustainable energy future. Low production of biohydrogen compared to the quantity of hydrogen produced by conventional is a main challenge which can be resolved by simultaneously replicating the process on pilot-scale. Biohydrogen is a novel research area, it was intriguing working with the waste and the possibility of biohydrogen production gives the insight for the future how food industries can innovate and work on the infrastructure to utilise the waste generated on the site to add value to the waste. The statistical tool response surface methodology used for process optimisation was helpful and eliminated the hassle and huge number of experiments.