Mitigation of ammonia and nitrous oxide emissions and cutdown of composting cycle during Enteromorpha prolifera composting with the co-addition of attapulgite and biochar

Abstract Since 2007, annual blooms of the green macroalga Enteromorpha prolifera have occurred in China’s coastal waters, posing serious threats to local aquaculture and ecological environment. Composting is an ideal way for managing E. prolifera waste. This study explored how attapulgite (AT) and biochar (BC) added individually or combinedly (AT-BC) affected ammonia (NH 3 ) and nitrous oxide (N 2 O) emissions, maturity and bacterial community during co-composting of E. prolifera and agricultural waste. Compared with the control and single AT or BC, AT-BC improved compost maturity and shortened composting cycle (from 60 to 15 d). AT-BC showed the lowest cumulative emissions of NH 3 and N 2 O, which were 35 and 20% lower than control, resulting in a 14 and 24% increase in the total nitrogen and nitrate nitrogen content, respectively. Furthermore, AT-BC reshaped the bacterial community composition, increased the co-occurrence network complexity and the proportion of negative links, suggesting that the composting system was more stable, which might be attributed to the keystone taxa, especially Bacillus . Furthermore, the promotion of nitrification and inhibition of denitrification process were the possible microbial mechanisms driven the deceleration of NH 3 and N 2 O release after co-addition of AT and BC. This study provides a promising strategy for the resourceful utilization of E. prolifera as organic fertilizer, with lower nitrogen loss and reduced environmental impact.