A shift from fossil fuels to renewable energy sources is essential to reduce global greenhouse gas emissions and climate change effects. Biofuels represent a promising low-carbon alternative for sectors that are hard to electrify, such as freight transport or aviation. This work investigates possible pathways for increasing the value of biomass at a Kraft pulp mill, focusing on black liquor and bark streams. Mathematical programming is coupled with superstructure optimization and systematic solution exploration to identify meaningful process configurations. The analysis of solutions under market variations allows for the identification of robust and competitive configurations for the co-production of pulp and fossil fuel alternatives. The results show that the integration of biorefineries in pulp mills results in better resource use and higher energy efficiency - diversifying the product portfolio and providing bio-based fuel products to the market while being economically viable. By incorporating fuel production in the conventional Kraft process, the carbon conversion efficiency of the mill can be increased from 48% to up to 67%. Extending the analysis, up to 2% of the European road freight transportation fuel could be provided with combined pulp and fuel production, and 5% of the worldwide fuel demand for passenger aviation.
Biomass, bioenergy and negative emission technologies are inherent to the future design of energy systems. Urban clusters have a growing demand for fuel, heat and electricity, which is both a challenge and an opportunity for biomass-based technologies. Their deployment should meet demand, while minimizing environmental impact and staying cost-competitive. We develop a systematic approach for the design, evaluation and ranking of biomass-to-X production strategies under uncertain market conditions. We assemble state-of-the-art and innovative conversion technologies, based on feedstock, by-products and waste characteristics. Technical specifications, as well as economic and environmental aspects are estimated based on literature values and industry experts input. Embedded into a bi-level mixed-integer linear programming formulation, the framework identifies and assesses current and promising strategies, while establishing the most robust and resilient designs. The added value of this approach is the inclusion of sub-optimal routes which might outperform competing strategies under different market assumptions. The methodology is illustrated in the anaerobic digestion of food and green waste biomass used as a case study in the current Swiss market. By promoting a fair comparison between alternatives it highlights the benefits of energy integration and poly-generation in the energy transition, showing how biomass-based technologies can be deployed to achieve a more sustainable future.
Electricity markets are currently experiencing a period of rapid change. The intermittent nature of renewable energy is disrupting the conventional methods used in operational planning of the electrical grid, causing a shift from a day-ahead forecast policy to a real-time pricing of delivered electric power. A path towards a more renewable, robust and intelligent energy system is inevitable but poses many challenges to researchers and industry. In the field of process industry, strategies based on demand side response are receiving attention and could represent a partial solution for this challenge. Coordination between production scheduling and procurement of electric power is of high importance and can contribute to reducing cost and emissions associated with production. A methodology to quantify such benefits is presented here with a case study, which reveals the potential benefits of flexible operation. In this case, the minimum compensation for flexibility services ranges between 5 and 20 € per unit (MWh) of restricted power. However, such a compensation depends on geographic location (electricity prices) and the frequency of restrictions. The method follows a rolling scheduling approach that provides optimization of the short-term schedule. This work introduces the concept of representing flexible processes as ‘equivalent batteries’ which store electricity from low-cost periods as intermediate products and consume the embedded energy during high-cost periods. Cost related to providing flexibility combined with the profits from optimized process scheduling contribute toward monetization of flexibility as an ancillary service for the grid. Balancing this service with the cost of implementing DSR solutions provides a means for calculating a pricing strategy for grid flexibility.
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