Biomass gasification is a widely used thermochemical process for obtaining products with more value and potential applications than the raw material itself. Cutting-edge, innovative and economical gasification techniques with high efficiencies are a prerequisite for the development of this technology. This paper delivers an assessment on the fundamentals such as feedstock types, the impact of different operating parameters, tar formation and cracking, and modelling approaches for biomass gasification. Furthermore, the authors comparatively discuss various conventional mechanisms for gasification as well as recent advances in biomass gasification. Unique gasifiers along with multi-generation strategies are discussed as a means to promote this technology into alternative applications, which require higher flexibility and greater efficiency. A strategy to improve the feasibility and sustainability of biomass gasification is via technological advancement and the minimization of socio-environmental effects. This paper sheds light on diverse areas of biomass gasification as a potentially sustainable and environmentally friendly technology.

Biomass is a promising renewable energy resource despite its low energy density, high moisture content and complex ash components. The use of biomass in energy production is considered to be approximately carbon neutral, and if it is combined with carbon capture technology, the overall energy conversion may even be negative in terms of net CO₂ emission, which is known as BECCS (bioenergy with carbon capture and storage). The initial development of BECCS technologies often proposes the installation of a CO₂ capture unit downstream of the conventional thermochemical conversion processes, which comprise combustion, pyrolysis or gasification. Although these approaches would benefit from the adaptation of already well developed energy conversion processes and CO₂ capture technologies, they are limited in terms of materials and energy integration as well as systems engineering, which could lead to truly disruptive technologies for BECCS. Recently, a new generation of transformative energy conversion technologies including chemical looping have been developed. In particular, chemical looping employs solid looping materials and it uniquely allows inherent capture of CO₂ during the conversion of fuels. In this review, the benefits, challenges, and prospects of biomass-based chemical looping technologies in various configurations have been discussed in-depth to provide important insight into the development of innovative BECCS technologies based on chemical looping.

In this paper, we compare and contrast the four most promising (i.e. commercially viable in the near future) technologies for the post-combustion capture (PCC) of CO₂ that can be retrofitted to a conventional pulverised-coal power plant. These are CO₂ capture using: (i) chilled ammonia, (ii) alkali-metal carbonates, (iii) membranes and (iv) calcium looping. These four technologies are compared to the benchmark monoethanolamine (MEA) scrubbing process in terms of efficiency penalty and cost indicators. We first review the relevant CO₂ capture chemistry and typical process flow schematics, and then discuss energy- and mass-balance considerations. We consider 18 published techno-economic studies on these technologies and highlight the key measures, including net CO₂ capture rate, net power output, net plant efficiency, capital costs, cost of electricity and cost of CO₂ avoided. Calcium looping technology results in the lowest efficiency penalty (4.6%-points) and cost of PCC (36.3% increase in levelised cost of electricity). In addition, the cost of CO₂ avoided by employing calcium looping for PCC can be as low as 29 USD₂₀₁₀ per tCO₂. On all three of these criteria, calcium looping performs more than twice as well as the benchmark MEA PCC process.

This paper reviews the advances of enhanced thermo-chemical processes applying H ₂ -selective membrane reactors and in situ CO ₂ capture for selective H ₂ production.