Pomace waste management scenarios in Québec--impact on greenhouse gas emissions

Physicochemical Properties of Dried and Powdered Pear Pomace

Pear pomace, a byproduct of juice production, represents a valuable reservoir of bioactive compounds with potential health benefits for humans. This study aimed to evaluate the influence of drying method and temperature on pear pomace, specifically focusing on the drying kinetics, grinding characteristics, color, phenolic profile (LC-MS/MS), and antioxidant activities of the powder. Drying using the contact method at 40 °C with microwave assistance demonstrated the shortest duration, whereas freeze-drying was briefer compared to contact-drying without microwave assistance. Freeze-drying resulted in brighter and more easily comminuted pomace. Lyophilized samples also exhibited higher total phenolic compound levels compared to contact-dried ones, correlating with enhanced antioxidant activity. Twenty-one phenolic compounds were identified, with dominant acids being quinic, chlorogenic, and protocatechuic. Flavonoids, primarily isoquercitrin, and rutin, were also presented. Pear pomace dried via contact at 60 °C contained more quinic and protocatechuic acids, while freeze-dried pomace at the same temperature exhibited higher levels of chlorogenic acid, epicatechin, and catechin. The content of certain phenolic components, such as gallic acid and epicatechin, also varied depending on the applied drying temperature.

Fruit Pomaces as Functional Ingredients in Poultry Nutrition: A Review

Sustainable poultry intensification is economically constrained by several factors including high feed costs, which constitute more than 70% of total production costs. Functional feed ingredients such as fruit pomaces can be incorporated into poultry diets as natural sources of nutrients and biologically active substances to deliver sustainable production. Fruit pomaces are agro-industrial waste by-products that have no direct food value for humans. Their utilization as feed ingredients would reduce feed-food competitions, optimize poultry production systems, and promote environmental, economic, and social sustainability. Large quantities of fruit pomaces are generated and disposed in landfills or through incineration with little regard to the environment. Thus, their inclusion in poultry feeds could offer a long-term strategy to protect the environment. Valorising fruit pomaces to enhance poultry production would also contribute toward sustainable development goals and food security through the provision of affordable high-quality protein to the rapidly growing human population. Moreover, the use of fruit pomaces complements food production systems by ensuring that food animals are reared on human inedible feedstuffs. Thus, this review explores the nutritional composition and subsequent feeding values of various fruit pomaces, while examining their environmental benefits when used as feed ingredients in poultry nutrition. Furthermore, strategies that can be employed to negate the effect of anti-nutritional factors in the pomaces are presented. We postulate that the use of fresh or valorised fruit pomaces would improve poultry production and significantly reduce the amounts of waste destined for incineration and/or direct deposition in landfills.

Strategies to Increase the Value of Pomaces with Fermentation

The generation of pomaces from juice and olive oil industries is a major environmental issue. This review aims to provide an overview of the strategies to increase the value of pomaces by fermentation/biotransformation and explore the different aspects reported in scientific studies. Fermentation is an interesting solution to improve the value of pomaces (especially from grape, apple, and olive) and produce high-added value compounds. In terms of animal production, a shift in the fermentation process during silage production seems to happen (favoring ethanol production rather than lactic acid), but it can be controlled with starter cultures. The subsequent use of silage with pomace in animal production slightly reduces growth performance but improves animal health status. One of the potential applications in the industrial context is the production of enzymes (current challenges involve purification and scaling up the process) and organic acids. Other emerging applications are the production of odor-active compounds to improve the aroma of foods as well as the release of bound polyphenols and the synthesis of bioactive compounds for functional food production.

Subcritical water hydrolysis coupled with hydrothermal carbonization for apple pomace integrated cascade valorization

This study evaluates an integrated biorefinery approach based on the waste hierarchy for the valorization of biodegradable waste, focusing on apple processing residues. Firstly, subcritical water hydrolysis was investigated at different experimental conditions (temperature 80 to 120 °C, dilution factor 10 to 30, residence time 10 to 30 min, initial pressure 10 to 30 bar) with the coincident aim of dissolving fermentable sugars and assess the effects of such treatment on the downstream solids. Secondly, spent solids were further processed by hydrothermal carbonization in the same reactor at fixed conditions (i.e., 180 °C, 3 h). The results showed that not only up to nearly 500 g kg_db^-1 of sugars are dissolved but also lignocellulosic structure is amended, improving products valorization potential. Depending on pretreatment conditions, the proposed approach can deliver hydrochar with potential either as soil amendment or for long-term applications, sustainably valorizing food waste.

Poultry litter stabilization by two-stage composting-vermicomposting process: Environmental, energetic and economic performance

Poultry litter (PL) is a heterogeneous mixture that contains bedding materials, antibiotics, dead skin, feed scraps, water, feathers and the resulting microbiota from poultry production cycle. Although its treatment does not receive attention, it is an important organic resource generated in the north-east region of Santa Fe Province since animal primary production is one of the main economic activities there and in the whole country. The objective of this work was to analyse the economic and energy aspects and the environmental impact of two scenarios corresponding to treat two different mixtures of organic wastes: Eucalyptus sp. sawdust (ES), rice hulls (RH) and PL. PL was considered in two different volume proportions: 1RH:3 PL for scenario 1 and 0.5RH:1 ES:2 PL for scenario 2. The two-stage combined system of composting + vermicomposting was applied to both scenarios and compared; on one hand, the current regulated practice for waste final deposition (landfill) and on the other hand, a base line scenario, which describes the current situation, where the raw material is transported and spread over the field as fertilizer without previous stabilization. The scenario construction was based according to on-site data, lab-scale experiments previously published and software databases. The environmental study was carried out with life cycle assessment; and the energy study, using cumulative energy demand methodology and the energy balance. Based on the results, it was possible to affirm the importance of the integrated agricultural waste treatment to address environmental benefits, especially related to the base line scenario. Furthermore, there were no significant differences between the two proposed scenarios. Economic and environmental results were contradictory when no long-term socio-economic consequences are considered. Combined composting and vermicomposting strategy reduce the organic matter and nutrients content not only to avoid discharges into the environment, but also to replace the fossil fuels consumption during unsustainable techniques as sanitary landfill, producing improved substrates for agricultural use.

Supplementation of Carbon-Based Conductive Materials and Trace Metals to Improve Biogas Production from Apple Pomace

Due to its high water and organic contents, management of apple pomace (AP) poses several waste management challenges on the apple juice and cider producing industries. Bioconversion of AP into biogas provides an excellent possibility to reduce the environmental challenge faced in the management of AP waste along with producing renewable energy in the form of methane. This study investigated the effect of carbon-based conductive materials (biochar and graphene) and trace metals supplementation to improve biogas production from AP. The results indicate that supplementation of biochar, trace metals, and graphene significantly improves the biogas production from AP. Trace metal and biochar supplementation at a COD concentration of 6000 mg/L resulted in 7.2% and 13.3% increases in the biogas production, respectively. When trace metals and biochar were supplemented together, the biogas production increased by 22.7%. This synergistic effect was also observed at the COD concentration of 12,000 mg/L. The improvement in the biogas formation was significantly higher for graphene supplemented reactors (27.8%). Moreover, biochar and trace metals supplementation also led to 19.6% and 23.0% increases in the methane yield relative to the reactor fed only with AP, respectively. These results suggest anaerobic digestion supplemented with carbon-based conductive materials and trace metals is a viable option for valorizing apple pomace.

Solid-State Fermentation (SSF) versus Submerged Fermentation (SmF) for the Recovery of Cellulases from Coffee Husks: A Life Cycle Assessment (LCA) Based Comparison

This article studies the environmental impacts of cellulase production by using a comparative attributional life cycle assessment (LCA) of two different scenarios of production. The first one is the commonly used submerged fermentation (SmF) using a pure substrate (cellulose powder) and a specific microorganism (Trichoderma reesei). The second scenario considers a novel system to produce enzymes and simultaneously treat a waste using the solid-state fermentation (SSF) process of coffee husk (CH) used as substrate. Experimental data were used in this scenario. The complete production process was studied for these two technologies including the fermentation phase and the complete downstream of cellulase. Life cycle inventory (LCI) data were collected from the database EcoInvent v3 (SimaPro 8.5) modified by data from literature and pilot scale experiments. The environmental impacts of both production systems revealed that those of SmF were higher than those of SSF. A sensitivity analysis showed that the results are highly conditioned by the energy use in the form of electricity during lyophilization, which is needed in both technologies. The results point to a possible alternative to produce the cellulase enzyme while reducing environmental impacts.

Adsorptive immobilization of agro-industrially produced crude laccase on various micro-biochars and degradation of diclofenac

Although enzymes are gifted with unique and unprecedented catalytic activity and selectivity over a wide range of pollutants, still their stability related issues often hinder their application in real environmental conditions. In this study, agro-industrially produced crude laccase was concentrated using ultrafiltration. Crude laccase was immobilized on pine wood (BC-PW), pig manure (BC-PM) and almond shell (BC-AS) biochar microparticles. Immobilization of laccase was investigated at various laccase activities on micro-biochars and the release (desorption) of the enzyme has been studied. It was observed that for all the biochars, as the initial concentration of laccase increased in the crude solution, the binding capacity and as result immobilization efficiency also increased. BC-PM was found to be the most effective (31.4 ± 3.1 U g^-1) at 10 U mL^-1 of enzyme activity followed by BC-AS (24.3 ± 4.8 U g^-1) and BC-PW (14.58 ± 3.3 U g^-1). In addition, the biochars were functionalized with citric acid for possible surface modifications and the effect of biochars for the adsorption of enzymes has been investigated. Isotherm studies of enzyme loading onto biochar established homogeneous monolayer adsorption as the major mechanism. The desorption of laccase from all biochars followed pseudo-second-order model. Immobilized laccase exhibited superior storage ability and shelf-life which were three times higher than free laccase. Finally, the immobilized laccase was used for the degradation of micropollutant, DCF and near 100% removal was obtained within 5 h at an environmentally relevant concentration (500 μg L^-1).

Microwave-assisted one-pot conversion of agro-industrial wastes into levulinic acid: An alternate approach

Brewery liquid waste (BLW), brewery spent grain (BSG), apple pomace solid wastes (APS), apple pomace ultrafiltration sludge (APUS) and starch industry waste (SIW) were evaluated as alternative feedstocks for levulinic acid (LA) production via microwave-assisted acid-catalyzed thermal hydrolysis. LA production of 204, 160, 66, 49 and 12 g/kg was observed for BLW, BSG, APS, APUS, and SIW, respectively, at 140 °C, 40 g/L substrate concentration (SC), 60 min and 2 N HCl (acid concentration). Based on the screening studies, BLW and BSG were selected for optimization studies using response surface methodology. Maximum LA production of 409 and 341 g/kg for BLW and BSG, respectively were obtained at 160 °C, 4.5 M HCl, 85 g/L SC and 27.5 min. Results demonstrated the possibility of using brewery wastes as promising substrates for economical and higher yield production of LA, a renewable platform chemical and versatile precursor for fuels and chemicals.

Conversion of apple pomace waste to ethanol at industrial relevant conditions

Apple pomace samples were evaluated for conversion to ethanol at industrial relevant conditions. Biomass degradation efficiency by commercial enzymes was evaluated at 20 % solid loading for dilute sulfuric acid, calcium oxide, and autoclave without any chemical (control) apple pomace samples. The control and calcium oxide-pretreated pomace provided similar sugar yields, while dilute sulfuric acid pretreatment resulted in reduced sugar yields. The control and calcium oxide-pretreated pomace hydrolysate were fermented to ethanol using a native Saccharomyces cerevisiae yeast strain, producing 38.8 and 36.9 g/L of ethanol, respectively. When control apple pomace sample loading was increased from 20 to 30 %, 57.5 and 50.1 g/L of glucose and fructose was produced, respectively. Lastly, we found that unhydrolyzed solids (UHS) present during fermentation had little effect on ethanol yield, as 53.6 and 53.8 g/L of ethanol were produced with and without UHS, respectively. Overall, ethanol yields were 134 g per kg of dry apple pomace. A complete process mass balance for enzyme hydrolysis and ethanol fermentation is provided in this manuscript. These results show that apple pomace is an excellent feedstock for producing ethanol that could be either used as biofuel or as beverage.

Anaerobic digestion of ultrasonicated sludge at different solids concentrations - Computation of mass-energy balance and greenhouse gas emissions

Two cases of anaerobic digestion (AD) of sludge, namely (i) with pre-treatment and (ii) without pre-treatment, were assessed using mass-energy balance and the corresponding greenhouse gas (GHG) emissions. For a digestion period of 30 days, volatile solids degradation of the control sludge and the ultrasonicated secondary sludge was 51.4% and 60.1%, respectively. Mass balance revealed that the quantity of digestate required for dewatering, transport and land application was the lowest (20.2 × 10(6) g dry sludge/day) for ultrasonicated secondary sludge at 31.4 g TS/L. Furthermore, for ultrasonicated secondary sludge at 31.4 g TS/L, the maximum net energy (energy output - energy input) of total dry solids (TDS) was 7.89 × 10(-6) kWh/g and the energy ratio (output/input) was 1.0. GHG emissions were also reduced with an increase in the sludge solids concentration (i.e., 40.0 g TS/L < 30.0 g TS/L < 20.0 g TS/L). Ultrasonication pre-treatment proved to be efficient and beneficial for enhancing anaerobic digestion efficiency of the secondary sludge when compared to the primary and mixed sludge.

Anaerobic digestion of thermal pre-treated sludge at different solids concentrations--Computation of mass-energy balance and greenhouse gas emissions

The effect of thermal pre-treatment on sludge anaerobic digestion (AD) efficiency was studied at different total solids (TS) concentrations (20.0, 30.0 and 40.0 g TS/L) and digestion times (0, 5, 10, 15, 20 and 30 days) for primary, secondary and mixed wastewater sludge. Moreover, sludge pre-treatment, AD and disposal processes were evaluated based on a mass-energy balance and corresponding greenhouse gas (GHG) emissions. Mass balance revealed that the least quantity of digestate was generated by thermal pre-treated secondary sludge at 30.0 g TS/L. The net energy (energy output-energy input) and energy ratio (energy output/energy input) for thermal pre-treated sludge was greater than control in all cases. The reduced GHG emissions of 73.8 × 10(-3) g CO2/g of total dry solids were observed for the thermal pre-treated secondary sludge at 30.0 g TS/L. Thermal pre-treatment of sludge is energetically beneficial and required less retention time compared to control.

GHG emission control and solid waste management for megacities with inexact inputs: a case study in Beijing, China

This study advances an integrated MSW management model under inexact input information for the city of Beijing, China. The model is capable of simultaneously generating MSW management policies, performing GHG emission control, and addressing system uncertainty. Results suggest that: (1) a management strategy with minimal system cost can be obtained even when suspension of certain facilities becomes unavoidable through specific increments of the remaining ones; (2) expansion of facilities depends only on actual needs, rather than enabling the full usage of existing facilities, although it may prove to be a costly proposition; (3) adjustment of waste-stream diversion ratio directly leads to a change in GHG emissions from different disposal facilities. Results are also obtained from the comparison of the model with a conventional one without GHG emissions consideration. It is indicated that (1) the model would reduce the net system cost by [45, 61]% (i.e., [3173, 3520] million dollars) and mitigate GHG emissions by [141, 179]% (i.e., [76, 81] million tons); (2) increased waste would be diverted to integrated waste management facilities to prevent overmuch CH4 emission from the landfills.

Bio-conversion of apple pomace into fumaric acid in a rotating drum type solid-state bench scale fermenter and study of the different underlying mechanisms

Apple pomace was bio-converted into fumaric acid in a rotating drum type solid-state bench scale fermenter and bio-conversion mechanisms were uncovered.