Sustainable valorization of apple waste in a biorefinery: a bibliometric analysis

Abstract

This bibliometric study explored the scientific publications of apple waste over the period from 2000 to 2020, aiming to contribute to the sustainable development of the apple industry toward waste-biorefinery implementation, advocating a circular economy. The bibliometric study covered the publications' evolution, research areas, top-cited papers, international collaborative networks, top countries and journals. The results demonstrate that 628 documents (604 articles and 24 reviews) studied apple waste over the last 20 years, and the number of publications exponentially increased after 2010. The most used keywords revealed that the main studied topics in the field were associated with technologies to manage apple pomace, the main solid waste generated from juice production, demonstrating a research trend toward renewable energy and bio-based products. The bibliometric study indicated that the most productive countries are China, India and the USA. Apple waste could be an environmentally friendly feedstock for biorefinery design and implementation. The biorefinery could produce value-added products (polyphenols, pectin, sugars and essential oils) and bioenergy (ethanol, methane, electricity and heat) in different industrial arrangements. The main technological routes described in the literature have been associated with the production of lactic acid, xylitol, ethanol, bioactive compounds, xyloglucan, films, pectin, acetic acid, acetone-butanol-ethanol, emulsifiers and inulinase enzyme. In conclusion, this review contributes to the decision-making for the industrial implementation of a waste biorefinery, advocating circular economy transition based on the sustainable valorization of apple waste.

Apple pomace management by anaerobic digestion and composting: a life cycle assessment

“…66 Moreover, by-products such as apple pomace are cheap feedstocks that make the biorefinery attempt substantially more attractive, 7,26 obtaining space for different valorization routes, including fermentable sugars, 67 ethanol production, 68 functional compounds, plant fibers, food additives, pectin, acids and enzymes, among others. [69][70][71] A similar study with apple juice was conducted by Khanali et al, 72 focusing on the complete energy flow and LCA of apple juice production. However, a fair comparison is not possible because there are some differences between the studies.…”

“…The literature shows GHG mitigation by using the AD process with apple pomace, and this result is more significant for countries that use fossil energy 66 . Moreover, by‐products such as apple pomace are cheap feedstocks that make the biorefinery attempt substantially more attractive, 7,26 obtaining space for different valorization routes, including fermentable sugars, 67 ethanol production, 68 functional compounds, plant fibers, food additives, pectin, acids and enzymes, among others 69–71 …”

“…The literature mentions the difficulty in obtaining relevant data about apple pomace management and the importance of considering this waste within the circular economy. 85 Future perspectives include the evaluation of different pretreatment techniques that are economically and technically feasible to improve biogas and methane production. Characterization of the complete digestate and its evaluation for fertilizer application should be considered, as should its effects on apple production and the general economic effects of decreasing chemical fertilizer consumption.…”

“…Nevertheless, the focus of this study was to compare the scenario in which apple pomace is anaerobically digested and biogas is used for bioenergy recovery to a case where this pomace is composted. The literature mentions the difficulty in obtaining relevant data about apple pomace management and the importance of considering this waste within the circular economy 85 …”

Bridging the Implementation Gap between Pomace Waste and Large-Scale Baker’s Yeast Production

“…Green extraction of bioactive compounds: [49][50][51][52][53] -extraction of pectin [6,[25][26][27][28]49,50,[54][55][56][57][58][59][60] -extraction of polyphenols [6,49,58] As solid biofuel [25,27,28] As source of dietary fiber (used in baked food products) [61][62][63] As functional ingredient in food products: [6] -bakery products [6,26,58,60,64,65] -meat products [6,50,54,64,[66][67][68] -dairy products [6,24,61,69] In the production of citric acid [6,26,[70][71]...…”