Anaerobic digestion of lignocellulosic biomass: challenges and opportunities.

Background Wine production represents one of the major agricultural activities worldwide. This production is accompanied with the generation of tremendous amounts of wastes and by-products exceptionally rich in bioactive compounds (especially phenolics). Recovering these molecules constitutes a key point for the valorization of the wine-processed materials, making them on the verge of commercialization. Regarding the health related benefits of these molecules; they could be used as additives for food and cosmetic products. Scope and approach The current review is revising the potential of alternative extraction methodologies for the recovery of antioxidant bioactive compounds from winery wastes and by-products. Conventional (solid liquid extraction, heating, grinding, etc) and non-conventional (pulsed electric fields, high voltage electrical discharges, pulsed ohmic heating, ultrasounds, microwave-assisted extractions, sub- and supercritical fluid extractions, as well as pressurized liquid extraction) methods have been applied for the extraction of high-added value compounds from winery-processed materials. Key findings and conclusions Non-conventional technologies represent a promising tool to recover high-added value compounds from winery wastes and by-products. However, several parameters are influencing the choice of technology used to recover these compounds, such as the matrix being processed, the selectivity, the energy consumption, the equipment cost, and the value of the extract.

Green alternative methods for the extraction of antioxidant bioactive compounds from winery wastes and by-products: A review

Anaerobic digestion is considered a competitive source for the production of renewable energy as far as efficiency and cost are concerned. To evaluate the anaerobic biodegradability of an organic substrate such as feedstocks, a test known as biochemical methane potential (BMP) has been commonly used. Current worldwide interest in using different organic substrates for anaerobic bioconversion is growing but there is a lack of clear references and comparability as a result of multiple factors that affect BMP determination. Several batch methods have been used to determine the methane potential. However, these technical approaches vary significantly from one reported method to the next another. In this review, the research works on the influence of different parameters of BMP determination have been discussed for critical and comparative evaluation. In addition, the extensive literature previously published dealing with BMP assays has been compiled and summarized focusing on two main subjects: firstly, methane yields of substrates, and secondly, the description of the various experimental procedures used to achieve the reported data.

Anaerobic digestion of solid organic substrates in batch mode: An overview relating to methane yields and experimental procedures

In the agricultural sector of many European countries, biogas production through anaerobic digestion (AD) is becoming a very fast-growing market. AD is a simple and robust process that biologically converts an organic matrix into biogas and digestate, the latter corresponding to the anaerobically non-degraded fraction. So far, digestate has been mostly used at farm-scales for improving soils. However, its ever-increasing production induces problems related to transport costs, greenhouse-gas emissions during storage and high nitrogen content that constrains its use to land application only. Consequently, research on alternative valorisation routes to reduce its environmental impact and to improve the economical profitability of AD plants should draw increasing interest in the future. This review therefore focuses on the different alternatives of digestate valorisation, apart from land applications: (I) the use of the digestate liquor for replacing freshwater and nutrients in algae cultivation; (II) the use of solid digestate for energy production through biological (i.e. AD, bioethanol) or thermal processes (i.e. combustion, hydrothermal carbonization and pyrolysis); (III) the conversion of solid digestate into added-value products (char or activated carbons) through a pyrolysis process.

New opportunities for agricultural digestate valorization: current situation and perspectives

Production of energy from lignocellulosic biomass or residues is receiving ever-increasing interest. Among the different processes, dark fermentation for producing biohydrogen and anaerobic digestion for producing biomethane present considerable advantages. However, they are limited by the accessibility of holocelluloses that are embedded in the lignin network. The authors propose a review of works on the conversion of biomass into biohydrogen and biomethane with the comprehensive description of (a) biomass composition and features that may impact on its anaerobic conversion and (b) the impact of different kinds of pretreatment on these features and on the performance of biohydrogen and methane production.

Lignocellulosic Materials Into Biohydrogen and Biomethane: Impact of Structural Features and Pretreatment

Evaluation of the biogas productivity potential of some Italian agro-industrial biomasses

Thermal pre-treatment of solid fraction from mechanically-separated raw and digested slurry to increase methane yield

Residual biogas potential from the storage tanks of non-separated digestate and digested liquid fraction.

Ammonia (NH3) emissions were measured from pig and cattle slurry storage by means of the funnel technique on the slurry surface and floating wind tunnels. Emissions from farmyard manure (FYM) heaps were quantified by the large open dynamic chamber technique. The trials on slurry stores were carried out in all four seasons whereas those on FYM heaps were carried out in cold temperature conditions only. Emissions from cattle slurry ranged from 1 to 1.6 g [NH3] m−2 day−1 with slurry temperatures of 4.7 and 24.3 °C, respectively, whereas emissions from pig slurry ranged from 0.8 to 2.5 g m−2 day−1 with slurry temperatures of 6.0 and 25.5 °C, respectively. FYM heaps showed average emissions of 3.4 g[NH3] m−2 day−1, with losses ranging from approximately 4.4% to 7.4% of the total Kjeldahl nitrogen (TKN) content. Emissions of ammonia from animal waste storage correlated with slurry temperature and were dependent on the measuring method used. Results obtained by the wind tunnel were considered to be the most representative of losses under real environmental conditions and could be used for an investigation of the national inventory.

Research Paper: SE—Structures and Environment Ammonia emissions from farmyard manure heaps and slurry stores—Effect of environmental conditions and measuring methods

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E. Dinuccio

Papers

Evaluation of the biogas productivity potential of some Italian agro-industrial biomasses

Thermal pre-treatment of solid fraction from mechanically-separated raw and digested slurry to increase methane yield

Residual biogas potential from the storage tanks of non-separated digestate and digested liquid fraction.

Research Paper: SE—Structures and Environment Ammonia emissions from farmyard manure heaps and slurry stores—Effect of environmental conditions and measuring methods

Ammonia losses from the storage and application of raw and chemo-mechanically separated slurry