Hydrothermal Carbonization of Biomass for Energy and Crop Production

Abstract

Hydrothermal carbonization (HTC) is a thermochemical pretreatment process where biomass is treated under hot compressed water to produce hydrochar. Hydrochar is a stable, hydrophobic, friable solid product, which has a fuel value similar to that of lignite coal. Among its other advantages, its capability to handle wet feed makes the HTC process most attractive. The complex reaction chemistry of HTC offers a huge potential for producing a variety of products, from fuel to supercapacitors, from carbon nanospheres to low cost adsorbents, from fertilizers to soil amenders. Hydrochar opens possibilities for replacing coal in existing coal-power plants. Its high surface area and adsorption characteristics make it compatible for use in supercapacitors. Hydrochar also contains high amounts of stable carbon and other nutrients, which are essential for soil amendment. Moreover, the HTC process liquid, especially if a short retention time is used, contains potentially toxic substances like phenols, furfurals, and their derivatives, which open opportunities for anaerobic digestion to produce biogas. This review paper gives an overview of the HTC process parameters, reactions, and the use of hydrochar for energy and crop production.

An Innovative Agro-Forestry Supply Chain for Residual Biomass: Physicochemical Characterisation of Biochar from Olive and Hazelnut Pellets

“…The added value of biochar is also linked to other issues, such as those involving agricultural and environmental sustainability. As claimed by many studies [1,16], biochar as a soil amendment can improve soil health and increase agricultural productivity with further environmental benefits related to global warming mitigation [16,[48][49][50][51][52]. Based on our results, we intend to define an agro-forestry chain to use the residual waste biomass for the production of high quality biochar for agronomic and commercial purposes.…”

Evaluation of Integrated Anaerobic Digestion and Hydrothermal Carbonization for Bioenergy Production

“…Due to its hydrophobic characteristics, dewateribility of HTC biochar increases several times compared to raw digestate or even raw biomass. [14][15][16][17][18] Moreover, HTC biochar has fuel values similar to lignite coal 16,17 . However, cellulose and lignin partially degrade in the HTC environment 18 .…”

“…Figure 7 shows the hydrophobic behavior, and softness of HTC biochar. During HTC, the fibrous crystalline structures are destroyed and produce a soft amorphous carbon-rich HTC biochar 16,17,28 . It can be seen from Table 1 that the mass yield of digestate and raw straw derived HTC biochar are 43.4%, and 38.3%, respectively.…”

Appraisal of changes in sewage sludge management

“…If the processing parameters are severe enough for a sufficient time, the cell walls may be destroyed, making the proteins easily accessible to biological degradation (Ruiz-Hernando et al 2013). Reuse of waste heat (Speidel et al 2015) from combustion of biogas released in subsequent anaerobic fermentation (Reza et al 2014) makes the energy balance of the hydrothermal pretreatment positive and therefore financially attractive (Ruffino et al 2015). This practice, which has been transferred into the commercial sector only recently, results in many technological and economical advantages (Wirth et al 2015).…”