The Monthly Digest – Food Waste – April & May 2018

Food Waste and by-products

R & D abstracts – April & May 2018

Food waste as a source of value‐added chemicals and materials: a biorefinery perspective (review)

As the availability of fossil‐based resources declines, there is an impending necessity of finding alternative feedstock able to secure the production of fuels and chemicals. Exploitation of biomass as renewable source of chemicals is an attractive possibility, in particular the one derived from food waste (FW). Every year, large amounts of waste are generated within or at the end of the food supply chain at the consumers use stage and hence its valorisation attracts great attention. FW has proven a valuable feedstock for its exploitation to produce a wide array of intermediates and products with promising applications in industry, owing to their similar performance with respect to established products. These include organic acids and furans (generally used as platform chemicals to further products); polymers like bacterial cellulose, polyhydroxyalkanoates or chitin; biosurfactants; biolubricants; or nanoparticles. This overview covers the latest trends in chemical, enzymatic and biotechnological processes reported in literature on the production of these chemicals and materials, with a focus on the use of FW as raw material.

Esteban J and Ladero M (2018) International Journal of Food Science and Technology 53:1095-1108

Techno-economic and profitability analysis of food waste biorefineries at European level (review)

Food waste represents a potential source to produce value-added materials replacing the use of virgin ones. However, the use of food waste as feedstock in biorefineries is still at an early stage of development and studies assessing its economic viability at large scale are lacking in the literature. This paper presents a techno-economic and profitability analysis of four food waste biorefineries that use wastes from tomato, potato, orange, and olive processing as feedstock. The study includes the assessment of potentially available quantities of those waste flows in Europe. Due to the low technology readiness level of this kind of biorefineries, a screening methodology to estimate the investment and manufacturing costs as well as two profitability ratios (the return on investment and the payback time) was adopted. Results show that not all the waste feedstocks have the same potential. The most profitable options are those related to implementing fewer plants, namely concentrating the production and capitalising on economies of scale while being at risk of increasing externalities, e.g. due to logistics of the feedstocks.

Cristobal J et al (2018) Bioresource Technology 259:244-252

Valorisation of fruit and vegetable waste from open markets for the production of 2,3-butanediol (research)

The bacterial strain Enterobacter ludwigii FMCC 204 was selected as the most efficient 2,3-butanediol (BDO) producer among five strains when cultivated on glucosefructosemannosearabinosexylosegalactose and sucrose in shake flask cultures. Plums, apples and pears were used for the production of fermentation medium via sequential maceration, suspension in water and centrifugation to collect the supernatant. Sugar production from mixed vegetables was evaluated via sulphuric acid treatment leading to 65.8% (w/w) of hemicellulose hydrolysis yield at initial solid concentrations of 50 g/L (on a dry basis) treated with 3% (v/v) H2SO4. Fed-batch cultures of E. ludwidgii on fruit derived feedstock resulted in BDO concentration, yield and productivity of 50 g/L, 0.4 g/g and 0.41 g/L/h. BDO production from vegetable waste hydrolysates via fed-batch cultures led to BDO concentration of 17.6 g/L. This study demonstrated that fruit and vegetable wastes from open markets can be used as fermentation feedstocks for BDO production.

Liakou V et al (2018) Food and Bioproducts Processing 108:27-36

Experimental and feasibility assessment of biogas production by anaerobic digestion of fruit and vegetable waste from Joburg Market (research)

Substrate-induced instability of anaerobic digestion from fruit and vegetable waste (FVW) results in low biogas yield. In this study, substrate management through fruit to vegetable mix ratio in a two-stage semi-continuous digester was investigated as a pathway for optimality of yield. The experiment conducted over 105 days with 62.52 kg of FVWs sourced from Joburg Market, South Africa showed that a stable process was achieved at a fruit to vegetable waste mix ratio of 2.2:2.8. At this ratio, optimal organic loading rate ranged between 2.68 and 2.97 kg VS/m3-d which resulted in a specific biogas yield of 0.87 Nm3/kg VS with 57.58% methane on average. The results of the experimental study were used as a feasibility assessment for a full-scale 45 tonnes/d plant for Joburg Market considering three energy pathways. The plant will produce 1,605,455 Nm3/y of biogas with the potential for offsetting 15.2% of the Joburg Market energy demand. Conversion of all biogas to biomethane was the most economically attractive energy pathway with a net present value of $2,428,021, an internal rate of return of 16.90% and a simple payback period of 6.17 years. This route avoided the greenhouse gas emission of 12,393 tonnes CO2, eq. The study shows that the anaerobic digestion of FVWs as sole substrate is possible with financial and environmental attractiveness.

Masebinu SO et al (2018) Waste management 75:236-250

Process design and techno-economic analysis of an integrated mango processing waste biorefinery (research)

This study evaluated costs and profitability associated with mango processing waste biorefinery plant with the goal of generating wealth from waste. Three pathways were evaluated (i) Only Pectin recovery (PEP) (ii) Pectin and Seed Oil recovery (PSEP), and (iii) whole biorefinery with multiple products (WMB). A plant capacity of 10 tons/h was considered as a base case for analysis. Effect of biomass feed composition on product yields were also reported in this study. The PSEP was found to be the best alternative for mango waste utilization. The NPV, IRR and PEP were $41 million, 34% and 2.4 years, respectively. In case of PEP and WMB, NPVs were $14.2 and $43.2 million; IRRs were 20% and 26%, and PBP were 4.2 and 3.4 years, respectively. Sensitivity analysis showed that plant capacity, plant operating days, and raw material composition were most important factors that influenced plant economics. Selling price of main product i.e. pectin had a major influence on plant economics. The effect of raw material price fluctuation however, did not influence plant economics significantly.

Arora A et al (2018) Industrial Crops and Products 116:24-34

Anaerobic digestion of orange peel in a semi-continuous pilot plant: An environmentally sound way of citrus waste management in agro-ecosystems (research)

The management of residues of citrus processing involves economic and environmental problems. In particular, the uncontrolled disposal of citrus processing waste near production sites can have heavy impacts on air, soil, surface water bodies and groundwater. Anaerobic digestion has been proposed as a viable alternative for citrus waste valorisation, if some problems, linked to the biochemical processes, are overcome. Although many experimental tests have studied the inhibitory effects of the high essential oil content of orange peel on biomethanisation processes, fewer experiences have been carried out in continuous or semi-continuous pilot digesters, more similar to the full-scale biogas plants, using real orange peel. This study has evaluated the methane production through anaerobic digestion of industrial orange peel using a pilot plant (84 L) with semi-continuous feeding at increasing Organic Loading Rates (OLR) and essential oil (EO) supply rates (EOsr) until the complete process inhibition. Under mesophilic conditions, the highest daily specific methane yield was achieved at OLR of 1.0 gTVS L−1 d−1 and EOsr of 47.6 mg L−1 d−1. Partial inhibition of the anaerobic digestion was detected at OLR and EOsr of 1.98 gTVS L−1 d−1 and 88.1 mg L−1 d−1, respectively and the process irreversibly stopped when OLR and EOsr reached 2.5 gTVS L−1 d−1 and 111.2 mg L−1 d−1, respectively. Under thermophilic conditions, the cumulative methane production (0.12 L gTVS−1) was about 25% of that under mesophilic conditions (0.46 L gTVS−1). The thermophilic digestion was completely inhibited at lower OLR (1.98 gTVS L−1 d−1) and EOsr (88.1 mg L−1 d−1) compared to mesophilic conditions. This study confirmed the suitability of anaerobic digestion of orange peel for biomethane production (provided that the right management of the process is set), in view of an environmentally sound way of agricultural residues management in agro-ecosystems.

Zema DA et al (2018) Science of the Total Environment 630:401-408