Two types of plastic carriers low-density polyethylene (LDPET) and high-density polyethylene (HDPET) were used as a support material for biofilm formation during anaerobic co-digestion of agricultural wastes. LDPET and HDPET were added separately to different reactors containing binary substrates: corn straw and cauliflower leaves (G 1), corn straw and cow dung (G 2), while ternary substrates corn straw, cauliflower leaves, and cow dung were used in G 3. Reactors containing either HDPET or LDPET carriers supported the enhancement of biogas and biomethane. Maximum daily biomethane (333.43 and 368.35 mL/day) was achieved after HDPET addition to G1 and G2 at day 10 and 12, respectively. The accumulative biomethane were significantly enhanced (p < 0.05) by 17.14% and 23.52%, compared with reactors having LDPET carriers 11.89% and 5.53%, respectively. HDPET addition to ternary substrates (G 3) resulted in highest biomethane production (31.61%) and total solids (31.70%) and volatile solid (61.63%) removal. The major short-chain fatty acids (SCFAs) detected in all groups were acetic acid (4–5 g/L) and propionic acid (2–3 g/L), and their conversion to biomethane was the highest with HDPET. Scanning electron microscopy (SEM) analysis of the supporting materials showed that the plastic carriers support the biofilm formation especially in the case of HDPET. This study demonstrated that addition of cost-effective plastic carrier (HDPET) to anaerobic digestion system supported the formation of biofilm, leading to significantly increase in substrate utilization and biomethane production.

Graphical abstract

两种类型的塑料载体低密度聚乙烯（LDPET）和高密度聚乙烯（HDPET）用作农业废弃物厌氧共消化过程中生物膜形成的支撑材料。将LDPET和HDPET分别添加到包含二元底物的不同反应器中：玉米秸秆和花椰菜叶（G 1），玉米秸秆和牛粪（G 2），而三元基质玉米秸秆，花椰菜叶和牛粪在G 3中使用包含HDPET或LDPET载体的反应器支持沼气和生物甲烷的增强。在第10天和第12天分别将HDPET添加到G1和G2后，达到了最大的每日生物甲烷（333.43和368.35 mL /天）。累计生物甲烷是显著增加（p 与具有LDPET载体的反应器分别为11.89％和5.53％相比，<0.05）降低了17.14％和23.52％。将HDPET添加到三元底物（G 3）上可产生最高的生物甲烷气产量（31.61％），并去除总固体（31.70％）和挥发性固体（61.63％）。所有组中检测到的主要短链脂肪酸（SCFA）为乙酸（4–5 g / L）和丙酸（2–3 g / L），使用HDPET转化为生物甲烷的最高。支撑材料的扫描电子显微镜（SEM）分析表明，塑料载体支持生物膜的形成，尤其是在HDPET的情况下。这项研究表明，在厌氧消化系统中添加具有成本效益的塑料载体（HDPET）支持了生物膜的形成，从而大大提高了底物利用率和生物甲烷的产生。

图形概要