Low temperature anaerobic digestion is an energy efficient system, however few studies have determined the kinetics of the anaerobic digestion of food waste at those temperatures. This study determined the kinetics of a food waste anaerobic digestor with mesophilic inoculum at 20°C. The impact of acclimatation time was revealed. Then biochar and trace elements were employed to evaluate their impact at 20°C. It was shown that addition of the trace elements boosted the kinetic up to 114% of the control reactor. This study proved that different biochars have variable effect on the kinetics (here negative and neutral effect). The kinetic values were evaluated with a first order model and used to estimate a virtual factory. With 27 000 tons of biowaste /year influx and 80% expression of the maximum methane potential, a single stage psychrophilic was deemed unrealizable (Hydraulic Retention Time (HRT): 9.6 month with the experimental kinetics). However, promising results can be obtained with an adequate exterior temperature & substrate temperature couple. 

The constantly growing population places significant demands on more efficient foodproduction. Currently, an unsustainable amount of synthetic fertilizers is being used in anattempt to meet the increasing demand for food. This has major consequences in the form ofnutrient leakage into nearby surroundings, contributing to eutrophication. The Baltic Sea isone of the inland seas that has been severely affected, leading to a significant increase invegetation. This has resulted in more stranded algae and seagrass, also known as beachcast,accumulating on the beaches of Öland, forming large piles. The beachcast contains high levelsof nutrients and therefore risks contributing to further nutrient leakage if not managedproperly. Instead, the beachcast can be collected and used as natural fertilizer, thussubstituting today's synthetic fertilizers. In this way, its nutrient-rich composition is utilized,and the nutrients are returned to the soil.

For the nutrients to be available to plants, the beachcast is composted to allow mineralizationto occur. During decomposition, both physical and chemical parameters change, serving asindicators of the compost's maturity. The physical parameters examined in this study aretemperature and moisture content, while the chemical parameters considered are ammoniaemission, carbon/nitrogen-ratio and ammonium/nitrate-ratio. By co-composting beachcastwith other substrates, this study aims to investigate how the composting of beachcast isaffected by co-composting with sawdust and biochar to produce a suitable compost. Sincebeachcast has a low carbon/nitrogen-ratio, carbon-rich substrates were used with the intentionof increasing the ratio. The study was conducted as an experiment where three differentbeachcast-substrate mixtures were composted in rotating composters. The different treatmentsconsisted of pure beachcast, beachcast and sawdust and lastly, beachcast and biochar.

The results showed that some type of decomposition of the beachcast occurred during theobservation period of the composting experiment, however it is unclear what type ofdecomposition took place. Furthermore, no significant differences between any of thetreatments were observed during the studied period. Due to the absence of some results andthe uncertainty of which phase of the composting process was studied, no definitiveconclusions can be made. Despite this, beachcast is still considered a potential substitute forthe synthetic fertilizers used today. To enable this, future studies are required for continuedinvestigation of beachcast.

Red mud, a waste byproduct of aluminum production, is accumulating rapidly, with an estimated annual production of up to 175 million tonnes in 2022. The potential valorization of rare earth elements contained in red mud is significant, valued at approximately 4.3 trillion USD$. This makes red mud a highly underutilized resource for metal recovery. Additionally, traditional storage methods such as dry and wet stacking pose substantial environmental risks due to the fine particle size and high alkalinity of red mud, which could lead to severe environmental degradation and social ramifications in the event of storage failure.

In this study, charcoal was produced from the abundant and cost-effective biomaterial, Luffa cylindrica, using slow pyrolysis in a fixed bed reactor. A Central Composite Design (CCD) was employed to create an experimental set up to investigate the response of biochar yield and Iodine Number as a function of the operating parameters, pyrolysis temperature and time, in an interval of 400-600 °C and 60-90 minutes, respectively. The CCD results indicated a significant dependence on temperature for both yield and iodine number, with a confidence level of 0.9. The relative variance in charcoal yield with respect to pyrolysis time and temperature was much lower than that of the iodine number, at 21% versus 110%, respectively. The CCD model was subsequently optimized to maximize the iodine number, yielding an optimal response at 450 °C and 75 minutes.

The charcoal produced under optimal conditions underwent characterization using Scanning Electron Microscopy (SEM), Brunauer-Emmett-Teller (BET) and Raman spectroscopy. The analysis revealed that the charcoal exhibited modest porosity and structural disorder, with an intensity ratio (ID/IG) of 0.85.

Adsorption experiments were performed at a contact time of 24 h, under a constant stirring rate of 200 rpm, using both Luffa cylindrica derived charcoal and commercial activated carbon, which has a much higher surface area. The results elucidated that surface area was not the limiting factor in the adsorption experiment, as neither type of charcoal demonstrated significant adsorption of the investigated metals. Fourier Transform Infrared (FTIR) analysis indicated structural modifications and oxidation of the charcoal, suggesting that the investigated pH range could inhibit adsorption. The only species detected from adsorption were low amounts of chloride ions, indicating that limited affinity and charcoal deterioration were the primary limiting factors in the adsorption experiment. For future research, it is recommended to conduct charcoal adsorption experiments at higher pH levels and to explore methods to enhance the affinity between the charcoal adsorbent and metal species. One promising approach is to increase the surface-active groups (SOCs) on the charcoal, which have a high affinity for metal ions in aqueous solutions, using oxidizing media such as ozone or nitric acid.

Hydrogen (H₂) is a promising fuel to decarbonize hard-to-electrify sectors and help coun-tries achieve their climate goals. However, most hydrogen produced worldwide is obtained from non-abated fossil fuels, a depleting natural resource and the main contributor to cli-mate change. In the last decades, biomass-to-hydrogen technologies have been developing as an emerging solution to displace the use of fossil fuels in the hydrogen sector. However, the environmental sustainability of bioenergy systems must be evaluated from a life-cycle perspective to ensure a better environmental performance than the fossil counterparts they intend to replace. This study consists of a cradle-to-gate consequential LCA (cLCA) on the multi-stage biomass gasification process WoodRoll© developed by the Swedish company Cortus AB to evaluate the potential environmental consequences of deploying this technol-ogy to produce high-purity hydrogen fuel from wood chips. This study shows that the system under study can deliver low-carbon hydrogen fuel and significantly improve its environmen-tal performance by using the main hydrogen production plant’s by-product (residual gasi-fication biochar) in the steel-making industry to replace pulverized coal. However, further conclusions on other impact categories are challenging to draw due to the lack of comparable studies. This study also showcases the need for further research in methane emissions dur-ing wood chips storage and the carbon sequestration potential of residual biochars produced by multi-stage gasification processes.

Hard carbon is regarded as one of the most promising anode materials for sodium-ion battery. However, the ash content of the hard carbon anode inherited from the precursor have several negative impacts on the electrochemical performance of hard carbon. The traditional method utilizes strong inorganic acid washing to reduce the ash content of hard carbon. However, this method results in heavy environment pressure and safety hazards. Therefore, it’s necessary to exploring an alternative ash content removal method which is safer and environment friendly.

This project develops an environmentally friendly approach to remove ash from hard carbon by using acetic acid. This approach effectively reduces the ash content and enhances the electrochemical performance of the hard carbon anode. The ash content of hard carbon decrease from 1.57 wt% to 0.655 wt% after the 4 mol /L acetic acid treatment. The two-step treatment process also studied in this project and shows a better ash removal ability than one-step treatment process. The ash content of 4 mol /L acetic acid and 20 wt% KOH only 0.28 wt%. Furthermore, the electrochemical performance of the two- step treated hard carbon exhibits notable improvements, including enhanced initial Columbic efficiency (from 84.53% to 88.11%), reversible capacity (from 244.2 mAh g-1 to 280.8 mAh g-1). The long cycle performance of chemical treated hard carbon anode need further investigations in future studies.