Catchlight Energy LLC, 98063, Federal Way, WA, USA.
Biotechnol Biofuels. 2013 Jan 28;6(1):10. doi: 10.1186/1754-6834-6-10.
Woody biomass is one of the most abundant biomass feedstocks, besides agriculture residuals in the United States. The sustainable harvest residuals and thinnings alone are estimated at about 75 million tons/year. These forest residuals and thinnings could produce the equivalent of 5 billion gallons of lignocellulosic ethanol annually. Softwood biomass is the most recalcitrant biomass in pretreatment before an enzymatic hydrolysis. To utilize the most recalcitrant lignocellulosic materials, an efficient, industrially scalable and cost effective pretreatment method is needed.
Obtaining a high yield of sugar from recalcitrant biomass generally requires a high severity of pretreatment with aggressive chemistry, followed by extensive conditioning, and large doses of enzymes. Catchlight Energy's Sugar process, CLE Sugar, uses a low intensity, high throughput variation of bisulfite pulping to pretreat recalcitrant biomass, such as softwood forest residuals. By leveraging well-proven bisulfite technology and the rapid progress of enzyme suppliers, CLE Sugar can achieve a high yield of total biomass carbohydrate conversion to monomeric lignocellulosic sugars. For example, 85.8% of biomass carbohydrates are saccharified for un-debarked Loblolly pine chips (softwood), and 94.0% for debarked maple chips (hardwood). Furan compound formation was 1.29% of biomass feedstock for Loblolly pine and 1.10% for maple. At 17% solids hydrolysis of pretreated softwood, an enzyme dose of 0.075 g Sigma enzyme mixture/g dry pretreated (unwashed) biomass was needed to achieve 8.1% total sugar titer in the hydrolysate and an overall prehydrolysate liquor plus enzymatic hydrolysis conversion yield of 76.6%. At a much lower enzyme dosage of 0.044 g CTec2 enzyme product/g dry (unwashed) pretreated softwood, hydrolysis at 17% solids achieved 9.2% total sugar titer in the hydrolysate with an overall sugar yield of 85.0% in the combined prehydrolysate liquor and enzymatic hydrolysate. CLE Sugar has been demonstrated to be effective on hardwood and herbaceous biomass, making it truly feedstock flexible.
Different options exist for integrating lignocellulosic sugar into sugar-using operations. A sugar conversion plant may be adjacent to a CLE Sugar plant, and the CLE Sugar can be concentrated from the initial 10% sugar as needed. Concentrated sugars, however, can be shipped to remote sites such as ethanol plants or other sugar users. In such cases, options for shipping a dense form of sugars include (1) pretreated biomass with enzyme addition, (2) lignocellulosic sugar syrup, and (3) lignocellulosic sugar solid. These could provide the advantage of maximizing the use of existing assets.
除农业残留物外，木质生物质是美国最丰富的生物质原料之一。可持续收获的残留物和间伐物估计每年约有 7500 万吨。这些森林残留物和间伐物每年可生产相当于 50 亿加仑的木质纤维素乙醇。在酶水解之前，软木生物质是预处理中最顽固的生物质。为了利用最顽固的木质纤维素材料，需要一种高效、可工业放大和具有成本效益的预处理方法。
从顽固的生物质中获得高糖产量通常需要用强烈的化学物质进行高强度预处理，然后进行广泛的调理，并使用大量的酶。Catchlight Energy 的 Sugar 工艺，即 CLE Sugar，使用低强度、高通量的亚硫酸盐浆化预处理顽固的生物质，如软木森林残留物。通过利用久经考验的亚硫酸盐技术和酶供应商的快速进步，CLE Sugar 可以实现总生物质碳水化合物转化为单体木质纤维素糖的高收率。例如，未去皮的火炬松屑（软木）的生物质碳水化合物有 85.8%被糖化，去皮的枫木屑（硬木）的生物质碳水化合物有 94.0%被糖化。对于火炬松，糠醛化合物的形成量为生物质原料的 1.29%，对于枫木，糠醛化合物的形成量为 1.10%。在预处理软木的 17%固体水解中，需要 0.075 g Sigma 酶混合物/g 干燥预处理（未洗涤）生物质的酶剂量，才能在水解物中达到 8.1%的总糖浓度，以及预水解液加酶水解的总转化率为 76.6%。在酶用量低得多的情况下，即 0.044 g CTec2 酶产品/g 干燥（未洗涤）预处理软木，在 17%固体水解中，水解物中的总糖浓度达到 9.2%，在预水解液和酶水解的组合中，糖的总收率为 85.0%。CLE Sugar 已被证明对硬木和草本生物质有效，使其真正具有原料灵活性。
有多种选择可以将木质纤维素糖整合到使用糖的操作中。糖转化厂可以毗邻 CLE Sugar 厂，并且可以根据需要从初始的 10%糖浓缩 CLE Sugar。然而，浓缩的糖可以运送到乙醇厂或其他糖用户等偏远地点。在这种情况下，运输糖的密集形式的选择包括：（1）添加酶的预处理生物质，（2）木质纤维素糖浆，和（3）木质纤维素糖固体。这些可以提供最大限度利用现有资产的优势。
