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Climate change is challenging human life and infrastructures by modifying the environment in which we live at a difficult-to-adapt rate. The transition to a low carbon and sustainable society is key to avoid a further decline of the climate and the environment and can be achieved by adopting renewable energy sources. The necessary increase in renewable energy production faces challenges like identifying cost effective power storage solutions and adapting to inadequate electricity grid infrastructures. Renewable energy, however, cannot be the only solution for sectors that are hard to electrify. Green hydrogen from renewable-based electricity can represent a solution for decarbonization. Hydrogen, produced from renewable resources, storable, and with a high potential to replace fossil fuels in the most energy intensive, hard-to-decarbonize and polluting applications, can play a pivotal role in climate change mitigation.

Consolidated bioprocessing (CBP) is characterized by a single-step production of value-added compounds directly from biomass in a single vessel. This strategy has the capacity to revolutionize the whole biorefinery concept as it can significantly reduce the infrastructure input and use of chemicals for various processing steps which can make it economically and environmentally benign. Although the proof of concept has been firmly established in the past, commercialization has been limited due to the low conversion efficiency of the technology. Either a native single microbe, genetically modified microbe or a consortium can be employed. The major challenge in developing a cost-effective and feasible CBP process is the recognition of bifunctional catalysts combining the capability to use the substrates and transform them into value-added products with high efficiency. This article presents an in-depth analysis of the current developments in CBP around the globe and the possibilities of advancements in the future.

Biofuels policy instruments are important in the development and diffusion of biogas as a transport fuel in Sweden. Their effectiveness with links to geodemographic conditions has not been analysed systematically in studying biogas development in a less urbanised regions, with high potential and primitive gas infrastructure. One such region identified is Gävleborg in Sweden. By using value chain statistics, interviews with related actors, and studying biofuels policy instruments and implications for biogas development, it is found that the policy measures have not been as effective in the region as in the rest of Sweden due to different geodemographic characteristics of the region, which has resulted in impeded biogas development. In addition to factors found in previous studies, the less-developed biogas value chain in this region can be attributed particularly to undefined rules of the game, which is lack of consensus on trade-off of resources and services, unnecessary competition among several fuel alternatives, as well as the ambiguity of municipalities’ prioritization, and regional cultural differences. To strengthen the regional biogas sector, system actors need a strategy to eliminate blocking effects of identified local factors, and national policy instruments should provide mechanisms to process geographical conditions in regulatory, economic support, and market formation.

This case study investigates the potentials, greenhouse gas (GHG), and energy performance of forest residue biofuels produced by new and emerging production technologies, which are commercially implemented in Sweden for heavy transport. The biofuel options included are ethanol (ED 95), hydro-processed vegetable oil (HVO), and liquefied biogas (LBG) produced from logging residues in forestry and sawdust generated in sawmills. The calculated life cycle GHG emissions, based on the EU Renewable Energy Directive calculation methodology, for all three pathways are in the range of 6–11 g CO2eq./MJ, corresponding to 88–94% GHG emission reductions as compared to fossil fuel. Critical parameters are the enzyme configuration for ethanol, hydrogen supply systems and bio-oil technology for HVO, and gasifier size for LBG. The energy input is ranging from 0.16 to 0.43 MJ/MJ biofuel and the total conversion efficiency from the feedstock to biofuel, including high-value by-products (excluding heat), varies between 61 and 65%. The study concludes that the domestic biofuel potential from estimated accessible logging residues and sawdust is equivalent to 50–100% of the current use of fossil diesel in heavy-duty road transport in Sweden, depending on the biofuel production technology selected and excluding energy by-products. Thus, an expansion of forest-based biofuels is a promising strategy to meet the ambitious climate goals in the transport sector in Sweden.

In the last years, some companies have implemented a new transport sharing system in cities based on a one-way trip with electric scooters with the advantage that they can be parked wherever in the streets. Such an implementation has not been realized in Gävle until now. The main objective of this thesis is to study the impact of electric scooters (ES) to the environment and compare their emissions with other modes of transport. First, this thesis realize a study of the transport trends of people in the city of study, i.e. Gävle. Next, it is connected with a study of how a company like this will work in this city and which characteristics such as the operating area and the fleet number should it has. Finally, it is performed a full life cycle analysis of these scooters with the actual charging system and, also, how it would be if the actual collection and redistribution of the scooters at night is changed for a battery replacement. The main objective of that change is that the collectors will not need to collect the scooters at night in a big fueled vehicle and they will change it for a small EV or a simple bike in where carry the fully charged batteries. In addition, it has been calculated how the recycling of the batteries would affect to the total emissions compared with the disposal to the landfill. The LCA of the ES has been compared with EV and ICE cars in order to know how effects to the transport emissions the implementation of a rental scooter company. The total emission for kilometer of electric scooters are higher than EV but lower than ICE vehicles. The results show that electric scooters from a rental company are only reducing carbon emissions only if they replace car trips. At the moment that these scooters replace other modes of transport such as bus, bike or walking, it becomes a less clean option. Therefore, this company implementation does not reduce the CO2 emissions., Outgoing

Dilute acid (DA) pretreatment results in the formation of inhibitory compounds and pseudo-lignin along with the burden of unnecessary materials like ash, extractive, lignin or their condensed products that reduces the conversion efficiency of cellulose to monomeric sugar. Indian Oil Corporation Limited (IOCL) has developed a modified pretreatment (MP) in order to reduce the enzyme dosage during ethanol production. This method uses extraction of biomass in water and varying alkali concentration of 0.2, 0.4 and 0.5%, prior to pretreatment as a strategy to reduce the enzyme dosage and improve the ethanol yield. The environmental and economic impact of these MP scenarios in comparison with conventional pretreatment (CP) is studied. The ethanol production increases from 218 to 267 L using MP. The introduction of extraction step prior to DA pretreatment fulfills the objective of reducing enzyme dosage by 23–39%. However, overall life cycle assessment (LCA) results revealed that performance of MP2, MP3 and MP4 is on a negative side in all the environmental impact categories as compared to CP due to the use of alkali, where a huge amount of emissions are released during the production stage. Overall, MP1 using water as a media for extraction is the most environmentally suitable pretreatment process for ethanol production. Life cycle costing (LCC) results showed that cost of 1 L ethanol production could be lowered down from 0.87 to 0.70 United States Dollar (USD) using MP1 scenario. From an environment and economic perspective, it is recommended to use only water as an extraction media for biomass, as this can reduce the enzyme dosage, emissions and cost.

The aim of this work was to study the dilute acid pretreatment of rice straw (RS) and fermentable sugar recovery at high solid loadings at pilot scale. A series of pretreatment experiments were performed on RS resulting in >25 wt% solids followed by enzymatic hydrolysis without solid-liquid separation at 20 and 25 wt% using 10 FPU/g of the pretreated residue. The overall sugar recovery including the sugars released in pretreatment and enzymatic hydrolysis was calculated along with a mass balance. Accordingly, the optimized conditions, i.e. 0.35 wt% acid, 162 °C and 10 min were identified. The final glucose and xylose concentrations obtained were 83.3 and 31.9 g/L respectively resulting in total concentration of 115.2 g/L, with a potential to produce >50 g/L of ethanol. This is the first report on pilot scale study on acid pretreatment of RS in a screw feeder horizontal reactor followed by enzymatic hydrolysis at high solid loadings.

Cost of cellulases is a major impediment in commercialization of cellulosic ethanol. To reduce the enzyme doses for the production of fermentable sugars from rice straw (RS), a series of alkali conditioning experiments were conducted prior to dilute acid (DA) pretreatment. This approach resulted in removal of a majority of extractives, ash, acetic acid, and part lignin, and thus resulted in lowering pseudolignin formation thereby increasing enzymatic hydrolysis yields. Glucan hydrolysis of 69.8%, 74.0%, and 83.5% was obtained at 10 wt % water insoluble solid (WIS) using 8 FPU enzyme/g WIS of biomass conditioned using 0.2, 0.4, and 0.5 wt % alkali prior to pretreatment, which is 14–37% higher than the control (61.0%). The overall sugar recovery in these experiments were 69.2%, 70.2%, and 68.5% at 15 wt % WIS resulting in a sugar concentration greater than 120 g/L, which in turn can produce approximately 5–6% w/v ethanol concentration in fermentation broth. It was found that this approach resulted in a decrease of the enzyme consumption vis-a-vis the conventional process by 46.4% to recover the same amount of sugars. This lowering of enzyme consumption has resulted in net savings, after taking into account the cost of alkali used in the conditioning steps.

Cotton stalk is a holocellulose rich, inexpensive agricultural residue available in surplus without any competitive uses neither as food nor as animal fodder. These aspectshold high potential for cotton stalk as a biomass to be suitable for ethanol production. Dilute acid pretreatment conditions on bench scale have been optimized for cotton stalk by Response Surface Methodology (RSM) using Central Composite Design (CCD). Effect of four pretreatment process variables viz. temperature, acid concentration, time of reaction and stirring speed has been optimized for maximum enzymatic sugar release during the subsequent enzymatic saccharification. Under the optimized pretreatment conditions, i.e., temperature: 157. °C, acid concentration: 1.07% (w/w),and time: 20 min, enzymatic sugar releasewas found to be 684 mg/g of dry pretreated biomass. A correlation of hemicellulose removal and inhibitor formation with combined severity factor (CSF) was drawn. Mass balance carried out for the pretreatment step under optimized conditions resulted in 68.35 and 8.31% of xylose and glucose saccharificationyieldsrespectively. Subsequent enzymatic saccharification yieldsofglucose and xylose were 93.56 and 19.93% respectively. The overall saccharification yield integrating pretreatment and enzymatic hydrolysis of cotton stalk was 91.06%. Physicochemical characterization of native and pretreated biomass was carried out by compositional analysis, FT-IR and XRD revealing significant changes in biomassproperties responsible for improved saccharification efficiency.