Year-Round Storage Operation of Three Major Agricultural Crop Residue Biomasses by Performing Dry Acid Pretreatment at Regional Collection Depots

Commercial cellulosic biofuel operation requires a reliable, low-cost, and stable feedstock logistic system. One great challenge is its long-term storage at least for one harvest cycle (1 year for agricultural crop residues) with a minimum loss of bulky, geographically dispersed, inflammable, and easily degradable lignocellulosic biomass. This study conducted an investigation of year-round storage of the agricultural crop residue feedstock under the scenario of performing dry acid pretreatment at the distributed regional collection depots, instead of the central biorefinery plant. The dry acid pretreatment method provides a practical basis for the storage operation by its ability for high preservation of polysaccharide solids, highly compacted accumulation density, being free from wastewater generation, low capital investment, and low energy consumption. Three major agricultural crop residues (corn stover, wheat straw, and rice straw) were pretreated by dry acid pretreatment and then stored in their major planting regions under varying natural conditions of temperature, rain and snow fall, humidity, wind, and sunlight. The pretreated corn stover, wheat straw, and rice straw contained approximately 50% (w/w) of moisture, and their high water absorption capacity maintained the crop residues in solid and fine-particle forms without free wastewater generation and flammability. Meanwhile, the pretreated crop residues were of low pH value and contained various inhibitory compounds for microbial growth. The results show that the crop residue feedstocks were well preserved with negligible solid and fermentable sugar loss after year-round storage in different regions. The physical properties, chemical compositions, enzymatic hydrolysis yields, and ethanol fermentability were maintained essentially constant with a few positive exceptions such as the increased hydrolysis yield and reduced inhibitor content. A case study shows that the feedstock transportation cost of the long-term stored feedstocks under the scenario of dry acid pretreatment at collection depots was significantly reduced compared to that of the direct transportation of virgin crop residual feedstocks. This study provided an efficient and practical logistic system for large-scale biorefinery plants.

Automated summary

This study investigated the year-round storage of agricultural crop residue feedstock using dry acid pretreatment method at distributed regional collection depots. The results showed that the pretreated crop residues were well preserved with minimal loss and maintained consistent physical properties, chemical compositions, enzymatic hydrolysis yields, and ethanol fermentability. Dry acid pretreatment also significantly reduced transportation costs and provided an efficient logistic system for large-scale biorefinery plants.