An integrated approach for efficient biomethane production from solid bio-wastes in a compact system

Direct Medium-Chain Carboxylic Acid Oil Separation from a Bioreactor by an Electrodialysis/Phase Separation Cell

Medium-chain carboxylic acids (MCCAs) are valuable platform chemicals and can be produced from waste biomass sources or syngas fermentation effluent through microbial chain elongation. We have previously demonstrated successful approaches to separate >90% purity oil with different MCCAs (MCCA oil) by integrating the anaerobic bioprocess with membrane-based liquid-liquid extraction (pertraction) and membrane electrolysis. However, two-compartment membrane electrolysis unit without pertraction was not able to separate MCCA oil. Therefore, we developed a five-compartment electrodialysis/phase separation cell (ED/PS). First, we tested an ED/PS cell in series with pertraction and achieved a maximum MCCA-oil flux of 1.7 × 10³ g d^-1 per projected area (m²) (19 mL oil d^-1) and MCCA-oil transfer efficiency [100% × moles MCCA-oil moles electrons^-1] of 74% at 15 A m^-2. This extraction system at 15 A m^-2 demonstrated a ∼10 times lower electric-power consumption (1.1 kWh kg^-1 MCCA oil) than membrane electrolysis in series with pertraction (9.9 kWh kg^-1 MCCA oil). Second, we evaluated our ED/PS as a stand-alone unit when integrated with the anaerobic bioprocess and demonstrated that we can selectively extract and separate MCCA oil directly from chain-elongating bioreactor broth with just an abiotic electrochemical cell. However, the electric-power consumption increased considerably due to the lower MCCA concentrations in the bioreactor broth compared to the pertraction broth.

Brewer's Spent Grains-Valuable Beer Industry By-Product

The brewing sector is a significant part of the global food industry. Breweries produce large quantities of wastes, including wastewater and brewer’s spent grains. Currently, upcycling of food industry by-products is one of the principles of the circular economy. The aim of this review is to present possible ways to utilize common solid by-product from the brewing sector. Brewer’s spent grains (BSG) is a good material for sorption and processing into activated carbon. Another way to utilize spent grains is to use them as a fuel in raw form, after hydrothermal carbonization or as a feedstock for anaerobic digestion. The mentioned by-products may also be utilized in animal and human nutrition. Moreover, BSG is a waste rich in various substances that may be extracted for further utilization. It is likely that, in upcoming years, brewer’s spent grains will not be considered as a by-product, but as a desirable raw material for various branches of industry.

Swine manure valorization in fabrication of nutrition and energy

Renewable energy can boost the growing population's need and rapid budgetary development. To reduce fossil fuel consumption is the initial purpose of renewable and sustainable energy, producing valuable bio-based products. The fermenters, using for pretreatment of swine manure, and involvement of swine carcasses are reported to enhance organic loading rate followed by improved biogas yield on household digesters. The compositions such as animal residues, pathogenic microbes, pharmaceutical residues and nutrient compositions including undigested feed are still confused. Therefore, it is mandatory to optimize and stabilize anaerobic practice and digestate filtration purification for consequential fertilizer consumption. The effective bio-methane recovery from energy-rich compounds is challenging due to slow degradation procedures. The pretreatment procedure could enhance lipid depolymerization and improve anaerobic fermentation. This article deeply focuses on biodegradation of swine manure. The components of this manure were evaluated and established several approaches to improve biogas production. Furthermore, recycling of co-digestates was discussed in detail as fertilizer consumption including hygienic aspects of manure and pretreatment strategies of biomass residues. KEY POINTS: • Co-digestion of manure and carcasses enhance bio-methane production. • Removel of ammonia from biogas digester may improve bio-methane gas. • A strong antimicrobial influence has been reported on biogas production.

Nutritional, Energy and Sanitary Aspects of Swine Manure and Carcass Co-digestion

Renewable energy can assist the management of the effects of population growth and rapid economic development on the sustainability of animal husbandry. The primary aim of renewable energy is to minimize the use of fossil fuels via the creation of environmentally friendly energy products from depleted fossil fuels. Digesters that treat swine manure are extensively used in treatment systems; and inclusion of swine carcasses can increase the organic loading rate (OLR) thereby improving biogas yield and productivity on farms. However, the characteristics of the components including animal residues, proteins, lipids, remains of undigested feed items, antimicrobial drug residues, pathogenic microorganisms and nutrient contents, are complex and diverse. It is therefore necessary to manage the anaerobic process stability and digestate purification for subsequent use as fertilizer. Efficient methane recovery from residues rich in lipids is difficult because such residues are only slowly biodegradable. Pretreatment can promote solubilization of lipids and accelerate anaerobic digestion, and pretreatments can process the swine carcass before its introduction onto biodigesters. This review presents an overview of the anaerobic digestion of swine manure and carcasses. We analyze the characteristics of these residues, and we identify strategies to enhance biogas yield and process stability. We consider energy potential, co-digestion of swine manure and carcasses, physical, chemical, and biological pretreatment of biomass, sanitary aspects of swine manure and co-digestates and their recycling as fertilizers.

Microbial population dynamics in response to increasing loadings of pre-hydrolyzed pig manure in an expanded granular sludge bed

In recent years, pig manure (PM) has been regarded as a valuable substrate for energy and resource recovery via bioprocesses such as anaerobic digestion (AD), however, the efficiency of digesting raw PM is limited by the presence of refractory compounds. In this study, we applied a series of pretreatment on raw PM, consisting of subsequent thermochemical pretreatment, enzymatic hydrolysis, tyndallization and filtration. The liquid PM hydrolysates were fed to an expanded granular sludge bed (EGSB) for the production of biogas. The general performance and population dynamics of the EGSB reactor were assessed during an extended operational period of 339 days. An efficient and stable digestion process was achieved under high organic loading rates (OLRs) up to 21 kg-COD/(m(3)·d), agreeing with a sludge loading rate of 0.75 kg-COD/(kg-VSS·d), 1600 mg-NH4(+)-N/L and 17 mg/L of free ammonia nitrogen. The tyndallization decreased the total amount of active cells from 1 × 10(8) to 1 × 10(2) CFU/ml. Hence, bio-augmentation with pigs' intestinal microbiota was absent and the community dynamics were mainly credited to the composition of the substrate (i.e. PM hydrolysates) and the environmental conditions inside the reactor. The results showed the influence of both the seed community and the imposed loading rates on the evolutionary trajectory of the EGSB microbial community. Four bacterial genera (Clostridium, Cytophaga, Bacillus and Bacteroides) and two methanogenic genera (Methanosaeta and Methanobacterium) dominated the communities. An obvious shift from aceticlastic Methanosaeta to hydrogenotrophic Methanobacterium appeared when the OLR was increased to over 10 kg-COD/(m(3)·d).