• Energy Research

Current and future trends in the world population lead to the continuous growth of municipal waste volumes. Only in the EU-28 approx. 86 million tons of biowaste is produced yearly. On the other hand, the recent energy crisis calls for a fast transition towards more local and renewable energy sources. Most of this stream could be recycled through anaerobic digestion (AD) to produce energy and high-quality fertilizers. This paper presents a balance of dry anaerobic digestion of municipal biowaste based on three years of system monitoring in an industrial-scale AD plant. The results indicate that the average biogas production rate of 120 Nm3/ton of fresh waste can be achieved. Biogas utilization in combined heat and power (CHP) units leads to an overall positive energy balance at significantly reduced CO2 emissions. The overall CO2 emission reduction of 25.3–26.6% was achieved, considering that biogas utilization is environmentally neutral. Moreover, biowaste conversion allows digestate production to substitute mineral fertilizers in agriculture and other applications. It is beneficial for soil protection and a broader environmental perspective.

Current and future trends in the world population lead to the continuous growth of municipal waste volumes. Only in the EU-28 approx. 86 million tons of biowaste is produced yearly. On the other hand, the recent energy crisis calls for a fast transition towards more local and renewable energy sources. Most of this stream could be recycled through anaerobic digestion (AD) to produce energy and high-quality fertilizers. This paper presents a balance of dry anaerobic digestion of municipal biowaste based on three years of system monitoring in an industrial-scale AD plant. The results indicate that the average biogas production rate of 120 Nm3/ton of fresh waste can be achieved. Biogas utilization in combined heat and power (CHP) units leads to an overall positive energy balance at significantly reduced CO2 emissions. The overall CO2 emission reduction of 25.3–26.6% was achieved, considering that biogas utilization is environmentally neutral. Moreover, biowaste conversion allows digestate production to substitute mineral fertilizers in agriculture and other applications. It is beneficial for soil protection and a broader environmental perspective.

The fruit processing industry generates enormous amounts of byproducts, which are primarily removed through landfill or incineration. However, these processes cause carbon dioxide and methane emissions and release dioxin into the environment. The management of fruit processing byproducts is important for reducing the amount of food waste that is sent to landfills and for developing strategies through the reuse of these products for valorization and economic added value. Fruit processing byproducts are rich sources of bioactive compounds and fermentable and nonfermentable sugars. Therefore, these materials are very attractive feedstocks for developing integrated multifeed biorefineries that coproduce a wide range of natural products and bioenergy. The studies presented here have shown sustainable strategies for managing fruit processing byproducts via a biorefinery approach to achieve full valorization via a circular economy. The full valorization project proposed five main phases, namely, pretreatment, extraction, dark or aerobic fermentation, anaerobic digestion, and post-treatment, as well as two additional pathways to generate additional bioelectricity. When choosing the appropriate directions for the presented concept, a technoeconomic analysis should be carried out, considering the type of biomass and its availability at the site of the biorefinery and throughout the year of production. Applying the proposed concept of biorefineries in closed-loop technology is a promising way to enhance economic efficiency and decrease environmental influence in accordance with sustainable development.

The fruit processing industry generates enormous amounts of byproducts, which are primarily removed through landfill or incineration. However, these processes cause carbon dioxide and methane emissions and release dioxin into the environment. The management of fruit processing byproducts is important for reducing the amount of food waste that is sent to landfills and for developing strategies through the reuse of these products for valorization and economic added value. Fruit processing byproducts are rich sources of bioactive compounds and fermentable and nonfermentable sugars. Therefore, these materials are very attractive feedstocks for developing integrated multifeed biorefineries that coproduce a wide range of natural products and bioenergy. The studies presented here have shown sustainable strategies for managing fruit processing byproducts via a biorefinery approach to achieve full valorization via a circular economy. The full valorization project proposed five main phases, namely, pretreatment, extraction, dark or aerobic fermentation, anaerobic digestion, and post-treatment, as well as two additional pathways to generate additional bioelectricity. When choosing the appropriate directions for the presented concept, a technoeconomic analysis should be carried out, considering the type of biomass and its availability at the site of the biorefinery and throughout the year of production. Applying the proposed concept of biorefineries in closed-loop technology is a promising way to enhance economic efficiency and decrease environmental influence in accordance with sustainable development.

We propose a one-stage hydrothermal extraction of sugar beet pulp leading to effective co-production of pectin and neutral monosaccharides with a relatively high yield and satisfactory purity without the presence of an acidic catalyst. The optimal experimental design methodology was used for modelling and optimizing the yield of pectin and neutral monosaccharides. In good agreement with experimental results (R2 = 0.955), the model predicts an optimal yield of pectin (approx. 121.1 g kg−1 ± 0.47 g kg−1) at a temperature and time of about 118.1 °C and 21.5 min, respectively. The highest yield of the sum of neutral monosaccharides (approx. 82.6 g kg−1 ± 0.72 g kg−1) was obtained at about 116.2 °C and 26.4 min (R2 = 0.976). The obtained results are suitable for industrial upscaling and may provide an incentive to implement a new, environmentally friendly, simple, and effective method for treating waste product from the sugar refining industry, which has proved onerous until now.

We propose a one-stage hydrothermal extraction of sugar beet pulp leading to effective co-production of pectin and neutral monosaccharides with a relatively high yield and satisfactory purity without the presence of an acidic catalyst. The optimal experimental design methodology was used for modelling and optimizing the yield of pectin and neutral monosaccharides. In good agreement with experimental results (R2 = 0.955), the model predicts an optimal yield of pectin (approx. 121.1 g kg−1 ± 0.47 g kg−1) at a temperature and time of about 118.1 °C and 21.5 min, respectively. The highest yield of the sum of neutral monosaccharides (approx. 82.6 g kg−1 ± 0.72 g kg−1) was obtained at about 116.2 °C and 26.4 min (R2 = 0.976). The obtained results are suitable for industrial upscaling and may provide an incentive to implement a new, environmentally friendly, simple, and effective method for treating waste product from the sugar refining industry, which has proved onerous until now.

Waste solid residue from the hydrothermal extraction of pectin derived from sugar beet pulp was used as feedstock in the production of 5-hydroxymethylfurfural (5-HMF). The depolymerization of pectin-free sugar beet pulp (PF-SBP) to monosaccharides and their dehydration to 5-HMF were conducted in subcritical water using a batch reactor. The experimental design methodology was used in order to model the hydrothermal process and to optimize the operational parameters of the reaction, namely temperature and holding time. These parameters are required to achieve the highest yield of 5-HMF. The model predicts, in good agreement with experimental results (R2 = 0.935), an optimal yield of 5-HMF (of approximately 38% in relation to the cellulosic fraction content in the PF-SBP) at a temperature of 192.5 °C and a holding time of about 51.2 min. 5-HMF was successfully isolated from the reaction mixture using the liquid–liquid extraction method. The results are suitable for industrial upscaling and may become an incentive to introduce a new, environmentally friendly, uncomplicated, and efficient waste treatment method. The method would be used to treat products from the sugar refining industry, the treatment of which has proven to be problematic until now.