A biorefinery is a refinery that converts biomass to energy and other beneficial byproducts (such as chemicals). The International Energy Agency Bioenergy Task 42 defined biorefining as "the sustainable processing of biomass into a spectrum of bio-based products (food, feed, chemicals, materials) and bioenergy (biofuels, power and/or heat)". As refineries, biorefineries can provide multiple chemicals by fractioning an initial raw material (biomass) into multiple intermediates (carbohydrates, proteins, triglycerides) that can be further converted into value-added products. Each refining phase is also referred to as a "cascading phase". The use of biomass as feedstock can provide a benefit by reducing the impacts on the environment, as lower pollutants emissions and reduction in the emissions of hazard products. In addition, biorefineries are intended to achieve the following goals:
Supply the current fuels and chemical building blocks
Supply new building blocks for the production of novel materials with disruptive characteristics Creation of new jobs, including rural areas Valorization of waste (agricultural, urban, and industrial waste) Achieve the ultimate goal of reducing GHG emissions
Classification of biorefinery systems
Biorefineries can be classified based in four main features:
Platforms: Refers to key intermediates between raw material and final products. The most important intermediates are: Biogas from anaerobic digestion Syngas from gasification Hydrogen from water-gas shift reaction, steam reforming, water electrolysis and fermentation C6 sugars from hydrolysis of sucrose, starch, cellulose and hemicellulose C5 sugars (e.g., xylose, arabinose: C5H10O5), from hydrolysis of hemicellulose and food and feed side streams Lignin from the processing of lignocellulosic biomass. Liquid from pyrolysis (pyrolysis oil) Products: Biorefineries can be grouped in two main categories according to the conversion of biomass in an energetic or non-energetic product. In this classification the main market must be identified: Energy-driven biorefinery systems: The main product is a second energy carrier as biofuels, power and heat. Material-driven biorefinery systems: The main product is a biobased product Feedstock: Dedicated feedstocks (Sugar crops, starch crops, lignocellulosic crops, oil-based crops, grasses, marine biomass); and residues (oil-based residues, lignocellulosic residues, organic residues and others) Processes: Conversion process to transform biomass into a final product: Mechanical/physical: The chemical structure of the biomass components is preserved. This operation includes pressing, milling, separation, distillation, among others Biochemical: Processes under low temperature and pressure, using microorganism or enzymes. Chemical processes: The substrate suffer change by the action of an external chemical (e.g., hydrolysis, transesterification, hydrogenation, oxidation, pulping) Thermochemical: Severe conditions are apply to the feedstock (high pressure and high temperature, with or without catalyst).
The aforementioned features are used to classified biorefineries systems according to the following method:
Identify the feedstock, the main technologies included in the process, platform, and the final products Draw the scheme of the refinery using the features identified in step 1. Label the refinery system according by citing the number of platforms, products, feedstock, and processes involved Elaborate a table with the features identified, and the source of internal energy demand
Some examples of classifications are:
C6 sugar platform biorefinery for bioethanol and animal feed from starch crops. Syngas platform biorefinery for FT-diesel and phenols from straw C6 and C5 sugar and syngas platform biorefinery for bioethanol, FT-diesel and furfural from saw mill residues.
Economic viability of biorefinery systems
Techno-economic assessment (TEA) is a methodology to evaluate whether a technology or process is economically attractive. TEA research has been developed to provide information about the performance of the biorefinery concept in diverse production systems as sugarcane mills, biodiesel production, pulp and paper mills, and the treatment of industrial and municipal solid waste.