Abstract

Hydrothermal carbonization (HTC) is the method of choice to convert wet waste biomass to hydrochars. Their porous structure can serve as a microenvironment to plant-growth-promoting rhizobacteria (PGPR), supporting their growth, survival, and activities. As published work lacks the systematic compilation of pore characteristics of hydrochars related to bacterial colonization, we collect available data and elaborate on their dependence on the carbonization process conditions, feedstocks, and methodology of pore system characterization. Our analysis indicates a high abundance of pores sized between 1 and 20 μm relevant for the protection of PGPR from predators, and of nutrients and labile C in hydrochars supporting bacterial growth. In addition to the selection of optimized process parameters and feedstocks (240–260 °C, low feedstock pH, non-lignocellulosic biomass), adding mineral amendments prior to HTC offers opportunities for engineering hydrochars with an even larger share of pore space suited for bacterial colonization. Using the comprehensive literature on biochars, we demonstrate that the interior pore space in chars determines the potential to serve as an inoculum carrier to PGPR, thereby enhancing nutrient acquisition and protecting plants from diseases and abiotic stresses. The pore characteristics of hydrochars are comparable to biochars, and hydrochars are generally superior in providing a labile C reservoir that PGPR can readily access. We argue that HTC provides a cost-effective conversion route to produce PGPR vectors/carriers from wet (waste) biomass serving various environmental management objectives (waste recycling, soil fertility, soil remediation technologies) and circular bioeconomy (sustainable agriculture, substituting non-renewable carrier materials and fertilizers).

• Highlights

• We review the role of pore characteristics of hydrochars for bacterial colonization

• We identify opportunities for engineering hydrochars to provide favorable habitat conditions to PGPR

• 240–260 °C, low pH, non-lignocellulosic feedstocks, and adding mineral amendments increase the habitable pore space

• Hydrochars offer suitable pore characteristics and high labile C amounts and are promising PGPR carriers/vectors

摘要

水热碳化 (HTC) 是将湿废生物质转化为水炭的首选方法。它们的多孔结构可以作为促进植物生长的根际细菌 (PGPR) 的微环境，支持它们的生长、生存和活动。由于已发表的工作缺乏与细菌定殖相关的水炭孔隙特征的系统汇编，我们收集了可用数据并详细说明了它们对碳化过程条件、原料和孔隙系统表征方法的依赖性。我们的分析表明，大小在 1 到 20 μm 之间的大量孔隙与保护 PGPR 免受捕食者以及水炭中支持细菌生长的营养物质和不稳定 C 有关。除了选择优化的工艺参数和原料（240–260 °C、低原料 pH、非木质纤维素生物质），在 HTC 之前添加矿物改良剂为工程水炭提供了机会，该水炭具有更大份额的适合细菌定植的孔隙空间。利用有关生物炭的综合文献，我们证明了炭的内部孔隙空间决定了作为 PGPR 接种载体的潜力，从而增强养分获取并保护植物免受疾病和非生物胁迫。水炭的孔隙特征与生物炭相当，并且水炭通常在提供 PGPR 可以轻松进入的不稳定 C 储层方面具有优势。我们认为 HTC 提供了一种具有成本效益的转化途径，可以从湿（废物）生物质中生产 PGPR 载体/载体，服务于各种环境管理目标（废物回收、土壤肥力、

• 强调

• 我们回顾了水炭的孔隙特征对细菌定植的作用

• 我们确定了工程水炭为 PGPR 提供有利栖息地条件的机会

• 240–260 °C、低 pH 值、非木质纤维素原料和添加矿物改良剂可增加可居住的孔隙空间

• Hydrochars 提供合适的孔特性和高不稳定的 C 量，是有前途的 PGPR 载体/载体