Search

Cellulose nanofibrils (CNFs) are typically produced via wet milling pretreatment method to facilitate efficient disintegration of cellulose fibers by pre-fibrillation and fiber size reduction. However, the use of high energy and presence of water during wet milling methods leads to the increase in overall energy consumption during CNFs production and pose challenges during storage and handling. The objective of this study is to investigate the dry grinding of cellulose fluff pulp using the shear cutting method to determine the specific energy required to produce cellulose precursors and their characteristics for manufacturing CNFs. The specific energy required to grind cellulose fluff pulp with a screen size of 0.25 mm in three cycles was measured. The ground sample received after each cycle was sampled to characterize its properties and its potential to produce CNF hydrogels. As the number of grinding cycles increased, the specific energy required per cycle decreased with an overall net energy consumption of 894 kWh/Mg for three grinding cycles. The cellulose powder from the third grinding cycle was successfully disintegrated into cellulose nanofibrils with an average diameter of 119 nm without any fiber clogging. In conclusion, the three-cycle shear cutting process was sufficient to produce dry cellulose precursors for CNFs production, while reducing the overall energy consumption and handling and storage problems. [ABSTRACT FROM AUTHOR]

Abstract: Thermal pretreatment or torrefaction of biomass under anoxic condition can produce an energy dense and consistent quality solid biomass fuel for combustion and co-firing applications. This paper investigates the fuel characteristics and grindability of pine chips and logging residues torrefied at temperatures ranging from 225°C to 300°C and 30min residence time. Grinding performance of torrefied biomass evaluated by determining energy required for grinding, particle size distribution and average particle size were compared with raw biomass and coal. Specific energy required for grinding of torrefied biomass decreased significantly with increase in torrefaction temperatures. The grinding energy of torrefied biomass was reduced to as low as 24kWh/t at 300°C torrefaction temperature. The gross calorific value of torrefied chips increased with increase in torrefaction temperature. Torrefaction of biomass clearly showed the improved fuel characteristics and grinding properties closer to coal. [ABSTRACT FROM AUTHOR]

Anaerobic Digestion (AD) is a well-developed sustainable technology to convert organic waste streams and energy crops to produce renewable gaseous biofuels, while recycling nutrients and mitigating greenhouse gas emissions. In this study, the environmental and economic impacts of an integrated-state AD technology (i -AD) producing Compressed Natural Gas (noted as BioCNG) were investigated from dairy-manure, food-wastes, and miscanthus biomass feedstocks, and compared with that of stand-alone liquid-state (LS-AD) and solid-state (SS-AD) AD technologies. A coupled life-cycle assessment and techno-economic analysis (LCA‐TEA) approach was used to estimate the Global Warming Potential (GWP) and the Minimum Selling Price (MSP) of BioCNG ‒ a renewable alternative to fossil-CNG. The results illustrated that the Fossil Energy Ratios (FERs) for BioCNG were between 2.3 and 3.3 in the increasing order as LS‐AD < i ‐AD < SS‐AD. The life-cycle GWPs to produce BioCNG via LS‐AD, SS‐AD, and i ‐AD were −5.1, −15.1, and −12.0 kgCO 2 eq/GGE (Gasoline-Gallon-Equivalent) respectively. The MSP of BioCNG (without incentives) via LS‐AD ($2.9/GGE) was lower than that of both SS‐AD ($4.1/GGE) and i ‐AD ($4.9/GGE). When the tipping-fee ($44/Mg), RIN(Renewable Index Number)-credit ($0.46/RIN), and carbon-credit($13.6/MgCO 2 eq) were considered, the MSP of BioCNG dropped by up to 70%, 45%, and 25% for LS‐AD, SS‐AD, and i ‐AD, respectively. Fungal-pretreatment of miscanthus had negligible impacts on the environmental and economic performances of BioCNG. Backhauling of solid-digestate for miscanthus cultivation may reduce the MSP, energy usage, and GWP by up-to 5%, 16%, and 7%, respectively. The commercial production of BioCNG from energy crops can potentially be competitive at a higher BioCNG market price or with favorable energy policies, financial support, and tax-benefits. Image 1 • BioCNG production of an integrated-state AD technology was studied. • The Global Warming Potential of BioCNG ranged from −5 to −15.0 kgCO 2 eq per GGE. • The Minimum Selling Price of BioCNG ranged from $3 to $5 per GGE without any credit. • The solid-state AD technology to produce BioCNG from miscanthus was very promising. • BioCNG through solid-state AD can be economical at a carbon price of $35/MgCO₂eq. [ABSTRACT FROM AUTHOR]

Abstract Storage is the critical operation within the biomass supply chain to reduce feedstock supply risks and to manage smooth year-around operations of a biorefinery or a bioenergy plant. This paper analyzed the economic and environmental impacts of four different biomass storage systems for woodchips (Outdoor-open, Outdoor-tarped, Indoor, and Silo) and two systems for pellets (Indoor and Silo). Storage cost includes the costs for handling (including ventilation in case of silo storage), infrastructure investment, and dry matter loss (DML) for each system. The estimation of total greenhouse gas (GHG) emissions includes the fugitive emissions from storage piles and emissions due to electricity and fuel consumption for each system. Among four storage systems, the outdoor-tarped ($15.0 ODMT−1, ODMT: Oven Dry Metric Ton) and silo ($5.8 ODMT−1) storage were the least-cost options for woodchips and pellets respectively. However, silo-storage could be the most promising option for storing woodchips ($5.8 ODMT−1) and pellets ($2.3 ODMT−1), if it is used for short-term (two months) and frequently (at least six times) in a year. The total GHG emissions for six-month storage were 2.8–11.8 kgCO 2 e ODMT−1 for woodchips and 8.6–42.0 kgCO 2 e ODMT−1 for pellets. During Outdoor-open storage, the lower heating value of woodchips could drop to 37% due to increased dry-matter loss (DML) and moisture content. The initial moisture content, bulk density, DML, and resource required during handling were the most sensitive parameters influenced the storage performances of both woodchips and pellets. This study has demonstrated that a combination of different storage options along the supply chain could reduce the total biomass storage cost for a biorefinery or power plant. Graphical abstract fx1 Highlights • Large-scale storage options for storing woodchips and pellets were studied. • The outdoor-open storage was the least-cost option for long-term storage of woodchips. • Bin/silo storage was the best option for short-term storage of woodchips and pellets. • The average bin storage cost ranged from 2 to 22 ODMT−1. • All storage systems had low energy use and GHG emissions. [ABSTRACT FROM AUTHOR]

Abstract Torrefaction of biomass improves the grindability of raw biomass by the transformation from a fibrous structure to a more brittle and friable, coal-like material. Torrefied biomass is a more desirable feedstock for co-firing applications, especially in existing coal-fired power plants. Therefore, measuring the grindability and the specific energy consumption are critical for understanding the comminution behavior of torrefied biomass, and thus selecting appropriate milling equipment. In this study, the effect of torrefaction temperature on the specific grinding energy consumption and the grindability of torrefied wood pellets and wood chips was investigated and compared with that of coal. The applicability of three well-known grinding equations (Kick, Rittinger and Bond) was studied for the torrefied biomass using a knife mill. The specific grinding energy of both torrefied wood chips and pellets linearly decreased with increased torrefaction temperature over a range of 250–290 °C. Rittinger's model was the best-fit for both wood chips (R2 = 0.72–0.90) and wood pellets (R2 = 0.67–0.76). When the intercepts were considered, the Rittinger's and Bond's equations fitted well with the experimental data (R2 = 0.79–0.99) for all torrefied biomass. The grindability of torrefied biomass was measured using the Hardgrove Grindability Index (HGI) and the International Organization for Standardization (ISO) grindability index. A relationship between the Bond Work Index (BWI), based on the Bond's theory and HGI was developed for wood chips and wood pellets. Contrary to HGI index, BWI decreased with an increase in torrefaction temperature. The grindability parameters developed for torrefied biomass can be used for modeling and selecting suitable milling equipment. Highlights • Specific grinding energy required for torrefied wood chips and pellets were determined • Grinding energy decreased linearly with increased torrefaction temperature (250–290 °C) • Rittinger's equation was fitted the best with grinding data for all torrefied biomass. • HGI and BWI for torrefied biomass produced at 290 °C were comparable to that of coal. [ABSTRACT FROM AUTHOR]