Comparative Evaluation of Industrial Hemp Cultivars: Agronomical Practices, Feedstock Characterization, and Potential for Biofuels and Bioproducts

Abstract

Industrial hemp has gained resurgent interest recently for applications in various sectors. This study evaluated 11 different industrial hemp [6 fiber-only and 5 dual-purpose (fiber and grain)] cultivars and compared their potential as a commodity crop for biofuel and bioproducts via combined agronomical, experimental, and economic analysis approaches. Composition analyses suggest large variations on the glucan, xylan, and lignin contents among the tested hemp cultivars while the theoretical ethanol yields ranged from 91 to 101 gallons/dry ton hemp stems predicted based on the glucan and xylan contents. Results from dilute acid pretreatment and enzymatic hydrolysis suggest practical ethanol yields of 70–91 gallons/dry ton hemp stems, with the highest ethanol yield of 91.1 gallons/dry ton hemp stems from the Futura 75 cultivar and the lowest of 70.6 gallons/dry ton hemp stems from the Codimone cultivar. Based on the agronomic data, the per hectare hemp stem biomass yield ranged from 2933 to 8340 kg for fiber-only cultivars and from 3582 to 7665 kg for the dual-purpose cultivars. In addition to the stems, field trial for the dual-purpose cultivars showed grain yields ranging from 555 to 1083 kg/ha. Preliminary cost analysis indicates that overall dual-purpose cultivars have advantages over fiber-only cultivars in terms of potential per hectare gross profit, with Bialobrzeskie and NWG 331 being the highest among all tested cultivars. These combined evaluations illustrate that industrial hemp has a significant potential to become a promising regional commodity crop for producing both biofuels and value-added products.

Recent Advancements in Biological Conversion of Industrial Hemp for Biofuel and Value-Added Products

“…Table 1 summarizes the chemical composition of industrial hemp biomass in the previous studies. The chemical composition of different industrial hemp cultivars was studied [13,24,25]. Each component showed wide ranges of composition: 32.6-51.1% of cellulose, 10.6-16.6% of hemicellulose, 14.6-29.4% of lignin, 2.6-7.6% of ash, 3.7-20.0% of extractives, and 0.3-23.1% of others.…”

“…Das et al also reported significant variation in hydrolysis yields of 11 hemp varieties pretreated under the same conditions. These observations could be attributed to the structural differences among various varieties that would result in different levels of biomass recalcitrance and accessibility of enzymes to the cellulose chains [13].…”

“…Many existing lignocellulosic biomass conversion strategies are applicable to convert the hemp biomass. Biological conversion through pretreatment followed by fermentation to ethanol, succinic acid, and others has been highlighted in recent studies (Figure 2b) [12,13,16]. Emerging global energy crisis and environmental issues such as global warming and marine pollution increase people's interest in renewable and sustainable resources and their applications.…”

“…The stem of hemp is composed of fiber and shiv and covered by bark [8]. The fiber and shiv have been used for paper and textile products and in the applications of animal bedding and construction materials, respectively [9][10][11]; however, the development of its applications in biofuels and biochemical applications were also studied due to its high carbohydrate contents [12,13].…”

Effect of lignin-blocking agent on enzyme hydrolysis of acid pretreated hemp waste

“…24 The increase in sugar yield depends on the pretreatment condition and its subsequent process in cellulolytic saccharication. Das et al (2020) found that both dilute acid (1% w/v H 2 SO 4 , 140 C for 30 min) and alkali (2% w/v NaOH, 140 C for 60 min) pretreatments were effective at obtaining a high glucose yield (>90%) from industrial hemp. 25 Similarly, an attempt with acid-assisted steam pretreatment (210 C with 2% SO 2 impregnation) for industrial hemp resulted in a high glucose yield of 89%.…”