Alkaline Pretreatment of Banana Stems for Methane Generation: Effects of Temperature and Physicochemical Changes

Abstract

The effects of NaOH pretreatment temperature on the physicochemical characteristics and methane production of anaerobically digested banana stems were investigated in this paper. With the increase of pretreatment temperature from 0 °C to 100 °C, the chemical oxygen demand (COD) of the soak liquid in the treated biomass approximately linearly increased from 5.9 g/L for the untreated stems to 34.0 g/L. A weight loss of 5.1% was observed for the untreated material, while it was up to 31.2% for the sample treated at 100 °C. The removal of lignin and hemicellulose accounted for the majority of the weight loss. The removal rates of lignin and hemicellulose increased from 15.0% to 41.6% and 1.9% to 23.6% when the treatment temperature increased from 0 °C to 100 °C, respectively. Moreover, the crystalline index (CI) of the banana stems also increased with rising temperature, resulting from the dissolution of amorphous cellulose with increasingly harsher alkaline environments. The optimal pretreatment temperature for banana stems was confirmed at 50 °C. In these conditions, methane was produced via anaerobic digestion with 239.9 mL/g total solid (TS) yield, which represented an increase of 66.7% over untreated banana stems.

Development of innovative pretreatments for simultaneous saccharification and citric acid production from banana pseudostem: bioprocess optimization and kinetic assessment.

“…Composition of various lignocellulosic biomass feedstocks. Fusarium oxysporum(Chen et al, 2017b. Therefore, utilizing this lignocellulosic biomass will minimize the aforementioned problems associated with it.…”

“…In South Africa, approximately 450 000 tons are produced yearly(Panigrahi et al, 2021). After the fruit is harvested, banana lignocellulosic biomass including rachis, foliage, and stems remain(Chen et al, 2017b). This waste is usually crushed and left to decompose on farms to replenish nutrients in the soil(Chen et al, 2017b).…”

“…After the fruit is harvested, banana lignocellulosic biomass including rachis, foliage, and stems remain(Chen et al, 2017b). This waste is usually crushed and left to decompose on farms to replenish nutrients in the soil(Chen et al, 2017b). However, this disposal method leads to environmental pollution in ground and water bodies resulting in the release of unpleasant greenhouse gases (hydrogen sulphide and ammonia gas) and the spread of Panama disease caused by the fungus production, animal feed production, organic fertilizer, renewable materials, wastewater purification and biofuel production(Chen et al, 2017b).…”

“…This waste is usually crushed and left to decompose on farms to replenish nutrients in the soil(Chen et al, 2017b). However, this disposal method leads to environmental pollution in ground and water bodies resulting in the release of unpleasant greenhouse gases (hydrogen sulphide and ammonia gas) and the spread of Panama disease caused by the fungus production, animal feed production, organic fertilizer, renewable materials, wastewater purification and biofuel production(Chen et al, 2017b). Banana pseudostem contains on average 42-60% cellulose, 19-23% hemicellulose and 15-17% lignin (Islam et al, 2019, Shimizu et al, 2018).…”