Biorefinery of food and beverage waste valorisation for sugar syrups production: Techno-economic assessment

Highlights

• Techno-economic study was conducted for F&B valorisation via integrated biorefinery.

• Fructose syrup, high fructose syrup, and glucose-rich syrup were the main products.

• By-products are proposed for various agricultural and industrial applications.

• Price of sugar syrups was the largest determinant of the profitability.

• Motivated demonstration for F&B industries adopting novel biotechnological processes.

Abstract

Techno-economic analysis was conducted to evaluate a food and beverage (F&B) waste valorisation process for sugar syrup production via integrated biorefinery. A comprehensive process model was developed with a capacity of 10 metric tons (MT) hour⁻¹ of food waste and 14 MT hour⁻¹ of beverage waste. Three scenarios were proposed with different types of sugar syrups as the main products: Scenario I) fructose syrup, Scenario II) high fructose syrup-42, and Scenario III) glucose-rich syrup. Mass balance showed conversion yields of 0.24 MT sugar syrups per MT of F&B waste, while lipids (0.07 MT per MT of F&B waste) and insect feed (0.44 MT per MT of F&B waste) were the co-products proposed to be used for other industrial biorefinery processes. All scenarios were observed to be economically self-sustainable with net profit generation (US$11-26 million year⁻¹) and positive net present values (US$92-294 million). Along with the net production costs (US$443-665 MT⁻¹), the sugar syrups derived from the F&B waste have relatively low minimum selling prices of US$157-747 MT⁻¹ at a 5% discount rate. Lastly, sensitivity analysis was performed which found that the prices of sugar syrups were the largest determinants of their profitability. This study proposes a significant techno-economic basis for F&B waste biorefinery, which offers a successful demonstration for food and drink industries adopting these biotechnological processes for the same plant size.

Introduction

In recent years, there has been a pressing need to find an alternative to petroleum refinery because of the limited reserves of non-renewable crude oil and severe pollution caused by oil refining. Biorefinery has been proposed as a promising replacement for more sustainable production of fuels, materials and chemicals by utilising renewable biomass and developing environmentally friendly technologies.

According to International Energy Agency Bioenergy Task 42, biorefinery is defined as “the sustainable processing of biomass into a spectrum of marketable products (food, feed, materials and chemicals) and energy (fuels, power and/or heat)” (IEA Bioenergy, 2012). It also indicates that biorefinery can be a concept, a facility, a process, a plant, or even a cluster of facilities, which integrate many different areas of knowledge encompassing chemical engineering, chemistry, biology and biochemistry, biomolecular engineering and other fields (IEA Bioenergy, 2012). Biorefinery is analogous to conventional oil refineries where multiple products and fuels are extracted and produced from petroleum nowadays. As stressed by the IEA, biorefinery does not only address our need for substitution with bio-based products having equivalent functional characteristics to fossil resource-derived products; it offers a unique advantage by addressing issues of sustainability in all aspects – economic, social and environmental. It employs renewable biomass as feedstock and decreases production costs through economies of scale and the development of green technologies to produce bio-based products. The variety of regionally based feedstocks and practices allows biorefinery to be flexible for application across the globe. Possible feedstocks that can be used in a biorefinery include sugar beet, black liquor, wheat, corn, wood, agricultural residues, sugar cane, surplus food, straw, and aquatic biomass, but also the biomass fraction of municipal solid waste. Among the biomass resources, valorisation of waste residues has great opportunities in biorefinery from the perspectives of waste treatment, nutrient recovery, and environmental pollution associated with improper waste disposal (Burange et al., 2016). Koutinas et al. (2014) presented integrated biorefinery for the first time to utilise various waste and by-product streams for restructuring the conventional manufacturing processes in food, pulp and paper and the first generation biofuel industries. Mohan et al. (2016) further summarised a number of waste-based biorefinery approaches and envisioned the change from a linear economy towards a circular economy by the adaptation of such integrated biorefinery in different industrial sectors.

There has been considerable interest in valorisation of food waste in biorefineries (Burange et al., 2016). Annual generation of food waste has surpassed 1.3 billion metric tons globally (Food and Agriculture Organization of the United Nations (FAO, 2011). In fact, a large proportion is wasted before consumption mainly because of insufficient purchase planning and stringent quality standards (Food and Agriculture Organization of the United Nations (FAO, 2011). A few reports revealed that most of the food and beverage (F&B) waste generated by the industry is edible and can be avoided (Hyman, 2009; Quested et al., 2013). Recent examples are the recovery of l-malic acid from beverage industrial wastewater using electrodialysis process (Lameloise et al., 2009,2012). Biorefinery is a novel approach to valorise F&B waste besides the conventional recycling technologies such as composting, anaerobic digestion and animal feed supplement. Intensive studies have been recently published by our group to evaluate the complexity and potential of F&B waste as biorefinery feedstock in terms of composition, volumes, and the possibilities to be converted into value-added products (Haque et al., 2017; Kwan et al., 2018a, 2018b; Yu et al., 2018). In general, F&B waste is composed of starch (30–60%, w/w), free sugars (10%, w/v), proteins (10%, w/w) and lipids (20%, w/w) (Kwan et al., 2018a; Ventura et al., 2011). Ventura et al. (2011) reported the sugar content of popular sweetened beverages mainly in the form of high fructose corn syrup (HFCS). These are ideal feedstocks in biorefinery for sugar production due to the high levels of starch and free sugars, but sugar refining processes must be applied thereafter to remove the impurities such as preservatives, colorants, caffeine, ions and soluble proteins (Kwan et al., 2018b). A bioconversion process was developed and successfully demonstrated at laboratory and pilot scales to recover fructose syrup and glucose-rich syrup from F&B waste by saccharification, adsorption, ion exchange chromatography, isomerisation, glucose-fructose separation using a simulated moving bed (SMB) system, and evaporation of sugar syrups (Kwan et al., 2018b; Yu et al., 2018). More than 89% of sugars were recovered from the hydrolysate yielding 0.14 kg of sugars per kg of F&B waste (Kwan et al., 2018b). The fructose syrup also conformed to the industrial requirements including appearance, fructose and glucose content, pH, sulphite ash, and the threshold limits for heavy metals and bacteria (Kwan et al., 2018b).

This study proposed a novel integrated F&B waste biorefinery through the production of different types of sugar syrups for various industrial processes. For example, the fructose syrup derived from F&B waste has been used for hydroxymethylfurfural (HMF) synthesis (Yu et al., 2018), which was proposed by Kaur et al. (2018) for bio-based production of polyethylene furanoate (PEF) and polyethylene terephthalate (PET) in the plastic industry. Kwan et al. (2016) also presented co-utilisation of glucose and fructose as carbon sources for fermentative lactic acid production with Lactobacillus casei Shirota, which demonstrated the feasibility of using glucose-rich syrup for fermentation processes. On the other hand, the by-product streams containing the other ingredients originating from F&B waste (e.g. proteins and lipids) have been utilised for the generation of value-added products. For example, Pleissner et al. (2015) and Karmee et al. (2015) harvested the lipids from restaurants’ leftovers and bakery waste for surfactants and biodiesel production, respectively. The remaining solids harvested after saccharification were used to feed insects (Hermetia illucens) to provide insect biomass as an alternative protein supply for the husbandry industry (Kwan et al., 2018a). By applying such integrated bioconversion processes, the F&B waste could be converted into various value-added products and useful feedstocks including:

• glucose and fructose syrups with different industrial applications, e.g. sweeteners such as HFS-42 (White, 2014), carbon sources in fermentation (Kwan et al., 2016), and bioplastics via HMF synthesis (Yu et al., 2018).

• lipids as feedstock for a wide spectrum of industrial processes, e.g. polyurethane as building materials (Kaur et al., 2018), biodiesel (Karmee et al., 2015), and surfactants (Pleissner et al., 2015).

• nutrient-rich solids & retentate as insect feed for alternative protein supply (Lin et al., 2017).

Although the technical feasibility of such integrated biorefinery has been proven by a number of laboratory studies, the economic aspect has never been explored. Therefore, a comprehensive techno-economic study is needed to (i) estimate the economic performance of the bioprocesses, (ii) identify the key process and economic factors and (iii) evaluate the investment risks. This techno-economic assessment is of significant importance for the long-term development and commercial success of F&B waste-based biorefinery. It may also develop new opportunities for various industries to adopt bio-based production by F&B waste-derived biomass, which will have a significant impact on the establishment of a circular bio-economy.

This study focused on techno-economic assessment to investigate the technical feasibility, profitability and extent of investment risk with regard to integrated biorefinery to achieve F&B waste valorisation. Three scenarios were proposed with different types of sugar syrups as the main products: Scenario I) fructose syrup; Scenario II) HFS-42; and Scenario III) glucose-rich syrup. The selections of these three types of sugar syrups were based on their potential applications in the industries. The reasons for selection of these three configurations are as follows: (I) Fructose syrup - as pointed out in our previous studies, PepsiCo Advanced Research Team – Sustainable Packaging in the US would like our research group to explore the technical feasibility for developing a bioconversion process to convert its expired F&B wastes to fructose syrup, which could be subsequently used for non-food packaging application (Kwan et al., 2018a, 2018b; Yu et al., 2018). (II) High fructose syrup (HFS-42) is a glucose-fructose mixture which would be considered as a second generation feedstock to be used in industrial biotechnology for production of biobased products (e.g. enzymes and organic acids). In this case, the sugars could be valorised without the requirement for isomerisation and glucose-fructose separation. Indeed, the assumption of selling glucose-fructose mixture to the current biotechnology industry has not been justified, but it is of interest to investigate the techno-economic performance and to compare the results with the production of fructose syrup. (III) Glucose-rich syrup – similar to HFS-42 in Scenario 2, glucose rich syrup can be directly sold as the main end-product to the industrial biotechnology without isomerisation and glucose-fructose separation. Since isomerisation did not take place, the major component of syrup should be glucose and the remainder should be fructose. It would be interesting to compare its techno-economic performance with the other two scenarios as significant cost reduction in downstream processing steps are anticipated in this scenario.

Process flowsheets have been developed for each scenario accompanied with the calculations of mass and utility balance. Lastly, sensitivity analysis was conducted to identify the key process and economic factors regarding the plant’s economy. To the best of our knowledge, this is the first study to focus on the techno-economic evaluation of F&B waste biorefinery.