Dilute sulfuric acid fractionation of Korean food waste for ethanol and lactic acid production by yeast

Enhanced Energy Recovery from Food Waste by Co-Production of Bioethanol and Biomethane Process

The primary objective of this research is to study ways to increase the potential of energy production from food waste by co-production of bioethanol and biomethane. In the first step, the food waste was hydrolysed with an enzyme at different concentrations. By increasing the concentration of enzyme, the amount of reducing sugar produced increased, reaching a maximum amount of 0.49 g/g food waste. After 120 h of fermentation with Saccharomyces cerevisiae, nearly all reducing sugars in the hydrolysate were converted to ethanol, yielding 0.43–0.50 g ethanol/g reducing sugar, or 84.3–99.6% of theoretical yield. The solid residue from fermentation was subsequently subjected to anaerobic digestion, allowing the production of biomethane, which reached a maximum yield of 264.53 ± 2.3 mL/g VS. This results in a gross energy output of 9.57 GJ, which is considered a nearly 58% increase in total energy obtained, compared to ethanol production alone. This study shows that food waste is a raw material with high energy production potential that could be further developed into a promising energy source. Not only does this benefit energy production, but it also lowers the cost of food waste disposal, reduces greenhouse gas emissions, and is a sustainable energy production approach.

As(III) adsorption onto Fe-impregnated food waste biochar: experimental investigation, modeling, and optimization using response surface methodology

Biochar derived from food waste was modified with Fe to enhance its adsorption capacity for As(III), which is the most toxic form of As. The synthesis of Fe-impregnated food waste biochar (Fe-FWB) was optimized using response surface methodology (RSM), and the pyrolysis time (1.0, 2.5, and 4.0 h), temperature (300, 450, and 600 °C), and Fe concentration (0.1, 0.3, and 0.5 M) were set as independent variables. The pyrolysis temperature and Fe concentration significantly influenced the As(III) removal, but the effect of pyrolysis time was insignificant. The optimum conditions for the synthesis of Fe-FWB were 1 h and 300 °C with a 0.42-M Fe concentration. Both physical and chemical properties of the optimized Fe-FWB were studied. They were also used for kinetic, equilibrium, thermodynamic, pH, and competing anion studies. Kinetic adsorption experiments demonstrated that the pseudo-second-order model had a superior fit for As(III) adsorption than the pseudo-first-order model. The maximum adsorption capacity derived from the Langmuir model was 119.5 mg/g, which surpassed that of other adsorbents published in the literature. Maximum As(III) adsorption occurred at an elevated pH in the range from 3 to 11 owing to the presence of As(III) as H₂AsO₃^- above a pH of 9.2. A slight reduction in As(III) adsorption was observed in the existence of bicarbonate, hydrogen phosphate, nitrate, and sulfate even at a high concentration of 10 mM. This study demonstrates that aqueous solutions can be treated using Fe-FWB, which is an affordable and readily available resource for As(III) removal.

Lactic acid production - producing microorganisms and substrates sources-state of art

Lactic acid is an organic compound produced via fermentation by different microorganisms that are able to use different carbohydrate sources. Lactic acid bacteria are the main bacteria used to produce lactic acid and among these, Lactobacillus spp. have been showing interesting fermentation capacities. The use of Bacillus spp. revealed good possibilities to reduce the fermentative costs. Interestingly, lactic acid high productivity was achieved by Corynebacterium glutamicum and E. coli, mainly after engineering genetic modification. Fungi, like Rhizopus spp. can metabolize different renewable carbon resources, with advantageously amylolytic properties to produce lactic acid. Additionally, yeasts can tolerate environmental restrictions (for example acidic conditions), being the wild-type low lactic acid producers that have been improved by genetic manipulation. Microalgae and cyanobacteria, as photosynthetic microorganisms can be an alternative lactic acid producer without carbohydrate feed costs. For lactic acid production, it is necessary to have substrates in the fermentation medium. Different carbohydrate sources can be used, from plant waste as molasses, starchy, lignocellulosic materials as agricultural and forestry residues. Dairy waste also can be used by the addition of supplementary components with a nitrogen source.

Pyrolysis of food waste over a Pt catalyst in CO2 atmosphere

In this study, a method of disposing food waste is introduced via catalytic pyrolysis under CO₂ condition. The catalyst and CO₂ hindered the generation of condensable compounds, leading to enhancing non-condensable gas generation. However, they did not affect the amount of solid residues left after the thermal reaction. The amount of condensable cyclic compounds was reduced when the catalyst and/or CO₂ were used. The enhancement of non-condensable gas production and reduction of cyclic compounds formation were maximized when the Pt catalyst and CO₂ were simultaneously applied to the pyrolysis of food waste. For instance, approximately 67.3 % less cyclic compounds, including benzene derivatives, were generated at 700 °C in the presence of the catalyst under a CO₂ atmosphere compared to non-catalytic conditions without CO₂. The results suggest that a CO₂-assisted catalytic pyrolysis is as environmentally benign disposal method for food waste.

Upgrading the organic fraction of municipal solid waste to poly(3-hydroxybutyrate)

The organic fraction of municipal solid waste was studied as feedstock for the production of poly(3-hydroxybutyrate) (P(3HB)). To release the monosaccharides, a diluted acid pre-treatment followed by an enzymatic hydrolysis was applied. A sugar yield of 49% was achieved using a pre-treated waste and an enzyme cocktail of Pentopan 500 BG and Celluclast BG. The addition of Glucoamylase NS 22035 helped to hydrolyze the starch fraction, improving the hydrolysis yield to 56%. The hydrolysate was used as culture medium to produce P(3HB) by Burkholderia sacchari DSM 17165. Assays at shaking flask scale showed that when the hydrolysate was used as substrate, the attained cell concentration was slightly higher than in the control medium. It was necessary to supplement the hydrolysate with extra glucose to increase the C/N ratio and with a mineral solution to overcome the nutritional deficiencies. The P(3HB) accumulation using the supplemented hydrolysate was 58% (g polymer/g biomass).