With a growing concern of climate change due to increased levels of CO2 in the atmosphere, carbon sequestration has been suggested as a possible solution for climate change mitigation. Biochar,a highly carbonaceous product produced through pyrolysis, is considered a viable option due to its content of stable carbon. This work covers the investigation of the possibility to produce biocharfrom four different feedstocks, namely peat, straw, horse manure and sewage sludge. The study includes a literature study and a five-week trial period at a 500 kW pilot plant, PYREG 500, in Högdalen. The thermal behaviour of the feedstocks, including garden waste, was investigated using thermogravimetric analysis (TGA). The TGA results were used to decide the optimal pyrolysis temperature for peat and straw at the pilot plant. The TGA results showed that the feedstocks behave differently when pyrolysed; the mass loss rate as well as the final mass loss varied. Physiochemical characterisation of the biochar was completed and the results were in agreement with previous studies. The produced biochar from straw and two types of peat had a C content above50 wt.% (76.6, 80.7, 79.2 wt.%) and low molar ratios of H/C (0.33, 0.36, 0.38) and O/C (0.032,0.023, 0.024). The pH increased as a consequence of pyrolysis and the biochars were alkaline (pH10.1, 8.5, 8.3). Polycyclic aromatic hydrocarbons (PAHs) were found in biochar from both strawand peat (8.26, 1.03, 5.83 mg/kg). In general, nutrients and heavy metals were concentrated in the biochar, except for Cd which decreased and Hg which could not be determined. The specific surface area of biochar from straw was considered small (21 m2/g) while biochar from peat had a higher specific surface area with a greater span (102-247 m2/g). The properties of the produced biochar were compared to the criteria included in the European Biochar Certificate and some of them were fulfilled, including the content of C, PAH and heavy metals. A flue gas analysis was completed when operating the pilot plant on straw pellets and it was showed that several emissions were released, including NO2, SOX, HCl and particulates, however, solely the emissions of NO2 exceed the regulations which will be applied in 2020. Regarding process design of a future pyrolysis plant, it is suggested that the means of material transport, particle separation, temperature control and quenching of biochar should be improved.

The aim of this project is to create a deeper understanding of biochar’s ability to adsorbnutrients. In the long run the aim is to find a way to use the most suitable structures of biocharfor a maximum adsorption of different kinds of nutrients. The objective of this project is tofind, through case studies and practical experiments, an effective method to examine andanalyze the structure of biochars and their ability to adsorb nitrates and phosphates.

The conclusion of the project was that analysis of the biochar’s ability to adsorb is a complexmatter. The BET-analysis is a good method to find the structure of the biochar. However, iodinenumber analysis could be a better alternative to directly find a value on the biochar’s ability toadsorb. The ICP-analysis of the solutions only works for phosphor, therefore spectroscopywould be a better alternative since it also can detect nitrogen and the different compounds.

The population growth as well as a rapid technical and economic development globally affects the energy consumption. This requires a secure, stable and sustainable supply of energy. Today fossil fuels dominate globally and this results in environmental problems. Fossil fuels are also a finite, unsustainable resource. Thus, there is a need to replace fossil fuels with sustainable alternative sources of energy. This is also central for environmental goals both in Sweden and in the European Union. There are expectations that processes for the conversion of lignocellulosic biomass to solid, liquid and gaseous fuels can contribute to a transition from fossil to renewable fuels. In this thesis, carried out in collaboration between KTH and IVL Swedish Environmental Research Institute, one of the conversion processes is investigated in detail – pyrolysis. Pyrolysis is a thermal process that converts lignocellulose under anaerobic conditions at temperatures between about 300-650°C. Three phases can be obtained as products. A volatile which can be condensed into pyrolysis oil, a solid which may be termed biochar or charcoal depending on the end use, and a gas phase. The yield and the quality of the products is dependent upon the type of raw material, the type of reactor and the process conditions. An examination of the status of different pyrolysis processes on or on the way to the market has been made. The current degree of commercialization and what the future may look like for both the technology and the products have been assessed through literature studies, internet searches, and interviews with selected companies and individuals with expertise in pyrolysis.

This report reveals that continuous pyrolysis is not yet a fully commercial process, but that it has the opportunity to reach commercialization during the right conditions. It is difficult to say when it occurs, due to various external factors, continued technical development, increased knowledge of the pyrolysis process and results of the current demonstrations. In this report, several critical factors for the commercialization of pyrolysis in Sweden have been identified, e.g. increased stability for policy instruments and that will limit the risk for investments (uncertainty and short-term decisions frightens investors) and the establishment of a value chain for the products, i.e. a stable market. Prices on fossil fuels and biomass feedstock are also important factors. Processes for the production of biochar is in the early stages of commercialization, and seem to have reached further in their development than processes for pyrolysis oil. The only fully commercial application of pyrolysis today is the production of charcoal that commonly is performed in traditional batch-wise processes. There are many possible uses for the products in which they have the potential to reduce carbon emissions and contribute to a more sustainable future. Standardization and certification of products is important, and demonstration of the use. Stabilization and further upgrading of pyrolysis oil is another important factor for commercialization. It seems like processes for catalytic upgrading are not yet sufficiently technically or financially developed to be able to provide a competitive product. Research and development in this area are ongoing. Integration of the process with incumbent industrial processes seems to be able to offer increased energy efficiency and reduced production costs.

Biochar has the potential to reverse the trend of increasing levels of carbon dioxide in the atmosphere. Biochar has soil&improving properties through its porous structure and large active area which can be used by agriculture, hobby cultivation and urban green structure. In an innovative project, Stockholm has set up a pilot plant for biochar&production incorporated into an urban flow that combines waste management, energy production, soil improvement and climate change mitigation. The purpose of this survey is to evaluate the importance of biomass processing because the amount of energy and resources invested in pre&treatment affects the overall sustainability potential of the project. Two different processed fractions of biomass were empirically investigated in the plant during the first months of operation. None of the tested fractions worked satisfactorily in operation. One contained too many small particles which caused problems with tunnel formation and feeding. The other fraction contained too many large pieces which caused repeated shutdowns. The analysis showed disproportionately high ash content in the second fraction's biochar. That may indicate combustion, which should be investigated further. 

This study is an analysis of the potential to have a slow pyrolysis power plant in Brista, Sweden. The study is investigating current technologies available and research and application of the pyrolysis products from the process. Pyrolysis has been known for over thousands of years. It has played an important part during the industrialization for producing coal in kilns. In recent years, the slow pyrolysis technology has started to become an area of interest because of the use and research surrounding the concept of biochar.Biochar is a term used to describe the char product of pyrolysis when biomass is used as a feedstock. The slow pyrolysis technology has a higher yield of char compared with other pyrolysis and carbonization methods. The biochar could be used as a soil enhancer to improve soil quality.Currently the biochar market is undeveloped and the concept is not well known in the general public. In Sweden there are no large scale slow pyrolysis processes for the production of biochar, in Europe there is some examples of slow pyrolysis power plant of various sizes. Slow pyrolysis has currently not been as profitable as traditional combustion of biomass. But it has the advantage to low grade feedstock sources and could become more profitable if the use and demand if biochar would increase.The profitability of establishing a slow pyrolysis plant is estimated by using the theoretical performance of such a plant. The slow pyrolysis processes used to create the model is based on the descriptions from the manufacturers Pyreg, Carbon Terra and BigChar. Data regarding the investment and operation cost of the plant is brought from manufacturers and other studies surrounding the slow pyrolysis concept. Different cost settings and fuel qualities for three different biomass types (Wood, forest residue and green garden waste) are applied to test the sensitivity of the process.The result of the study indicates the plants utilizing the green garden waste material will have the shortest payback period and return on investment. The green garden waste seem to be possible to use as a feedstock in a slow pyrolysis process to produce biochar of certifiable standard and large quantities are available in the area around Brista, but further research is needed.The larger reactor with a capacity of circa 3-5 MW had the highest return on investment and was not as sensitive to fluctuations of heat and biochar price as the smaller pyrolysis alternatives. The environmental benefit of establishing a slow pyrolysis power plant could not be determined. The char produced could work as a carbon sink if utilized as a soil enhancer. But the relatively small production capacity 0,5-5 MW makes the impact insignificant at a district level. But it could serve as a method to bring new research opportunities. New projects regarding biochar production in Sweden in under process and could bring new information that could improve the model of biochar production.