Axel Funke

Hydrothermal carbonization of biomass residuals: a comparative review of the chemistry, processes and applications of wet and dry pyrolysis

The carbonization of biomass residuals to char has strong potential to become an environmentally sound conversion process for the production of a wide variety of products. In addition to its traditional use for the production of charcoal and other energy vectors, pyrolysis can produce products for environmental, catalytic, electronic and agricultural applications. As an alternative to dry pyrolysis, the wet pyrolysis process, also known as hydrothermal carbonization, opens up the field of potential feedstocks for char production to a range of nontraditional renewable and plentiful wet agricultural residues and municipal wastes. Its chemistry offers huge potential to influence product characteristics on demand, and produce designer carbon materials. Future uses of these hydrochars may range from innovative materials to soil amelioration, nutrient conservation via intelligent waste stream management and the increase of carbon stock in degraded soils.

Heat of reaction measurements for hydrothermal carbonization of biomass

This paper presents a set of calorimetric measurements with the aim of better understanding the calorific nature of hydrothermal carbonization. Presented values so far show an inadequately high scatter to do so, preventing a well funded assessment of the energetic feasibility of this process. The heat released during hydrothermal carbonization at 240°C measured with the applied differential calorimetry setup is -1.06MJ/kg(glucose,daf) with a standard deviation of 14%, -1.07MJ/kg(cellulose,daf) with a standard deviation of 9%, and -0.76MJ/kg(wood,daf) with a standard deviation of 32%. These results are in good agreement with the theoretically derived maximum heat release. Despite the comparably high experimental standard deviation of these results, their accuracy is considerably higher than previously published results.

Fast pyrolysis char - Assessment of alternative uses within the bioliq® concept.

Experiments with a process development unit for fast pyrolysis of biomass residues of 10kgh(-1) have been performed to quantify the impact of two different product recovery options. Wheat straw, miscanthus and scrap wood have been used as feedstock. A separate recovery of char increases the organic oil yield as compared to a combined recovery of char and organic condensate (OC). Furthermore, it allows for an alternative use of the byproduct char which represents an important product fraction for the high ash biomass residues under consideration. The char produced shows little advantage over its biomass precursor when considered as energy carrier due to its high ash content. Significant value can be added by demineralizing and activating the char. The potential to increase the economic feasibility of fast pyrolysis is shown by an assessment of the bioliq® process chain.

Hydrothermal Carbonization of Biomass

Abstract From the very beginning, nature used hydrothermal processes to create fuels during various geological and biological eras involved in the formation of our planet. We then intensively used such fuels for societal development. Like any inheritance, we have the responsibility to pass them on to further generations. However, the rate at which we have used such nonrenewable fuels is enormous, despite their initial abundance. As a consequence, Earth’s environment today is in danger because of dramatic increase in CO 2 associated with burning fossil fuels . Although, as few as 300 years ago humans subsisted almost entirely on renewables, our habits have progressively changed, and by the end of the twentieth century we became 100% dependent on fossil fuels. Besides damaging the ecosystem, such fossil resources are unevenly distributed geographically, and therefore, the price of oil today bears no relationship to its production cost. We clearly need to move away from fossil fuels in order to prevent further damage of the planet. A viable and environmentally safe alternative to fossil fuels needs to be available for the future generations. As nature made fossil fuels hydrothermally, it makes sense to learn from such natural processes. Biomass is the most available renewable resource on Earth, and therefore it should become the main source for future renewable energy. In this chapter, we present an overview of sustainable and viable hydrothermal transformations of biomass into artificial coal and related materials, or hydrothermal carbon.

Fast Pyrolysis of Biomass Residues in a Twin-screw Mixing Reactor

Fast pyrolysis is being increasingly applied in commercial plants worldwide. They run exclusively on woody biomass, which has favorable properties for conversion with fast pyrolysis. In order to increase the synergies of food production and the energetic and/or material use of biomass, it is desirable to utilize residues from agricultural production, e.g., straw. The presented method is suitable for converting such a material on an industrial scale. The main features are presented and an example of mass balances from the conversion of several biomass residues is given. After conversion, fractionated condensation is applied in order to retrieve two condensates — an organic-rich and an aqueous-rich one. This design prevents the production of fast pyrolysis bio-oil that exhibits phase separation. A two phase bio-oil is to be expected because of the typically high ash content of straw biomass, which promotes the production of water of reaction during conversion. Both fractionated condensation and the use of biomass with high ash content demand a careful approach for establishing balances. Not all kind of balances are both meaningful and comparable to other results from the literature. Different balancing methods are presented, and the information that can be derived from them is discussed.