## 6 Conclusions  
RS generation will continue to increase as rice production continues to rise to provide food for a still growing global population. The AD of RS is a viable option for the recovery of energy and nutrients. The nutrients (N, P, and K) are mostly conserved in the digestate during the AD, and their significant portion is available in LD. The effective use of nutrients available in the digestate is a way to partially substitute fertilizers for the amendment of agricultural land.  
The AD of RS at thermophilic conditions results in higher biogas/methane yield and higher CH\({}_{4}\) content in biogas as compared to mesophilic conditions. In contrast, the mesophilic process is more robust and less sensitive to environmental changes. Using a suitable inoculum and co-substrate in an appropriate amount enhances biogas/methane yield in the AD of RS by providing nutrients balance, dilute toxic compounds, adjust moisture content, improve buffer capacity, and stability of the system. Optimal selection of mixing (speed, time, and intervals), OLR, recycling LD, and TEs (with appropriate amount) also enhances the biogas/methane yield.  
Pilot-scale plants and experiments are necessary to design and define operational parameters for farm-scale biogas plant treating RS. Technically, the implementation of farm-scale biogas plants utilizing RS together with other suitable substrates such as PWW or other livestock manure is possible. It will provide energy and nutrients recovery to the local farm. However, the economic feasibility of such a plant should be evaluated.  
[PERSON] reviewed the literature and wrote the first draft of the paper. [PERSON], [PERSON] reviewed and edited to enhance the scientific quality of the paper. All authors have read and agreed to the published version of the manuscript.  
[PERSON] is a doctoral student and funded by the Ministry of Higher Education Commission (HEC), Pakistan (SAP 50020935). This work was supported by the German Federal Ministry of Education and Research under the project \"BIORIST\"- A joint research project for an innovative process technology for biogas production from rice straw (01 LY1508A).  
The authors extend their thanks and gratitude to [PERSON] for providing critical constructive comments to improve the quality of this paper. We acknowledge support by the German Research Foundation and the Open Access Publication Fund of TU Berlin. Our sincere thanks for the two anonymous reviewers who provided critical constructive comments on the manuscript, which resulted in a significantly improved article.  
The authors declare no conflict of interest.  
**CS**: Corn stover/straw
**CSTR**: Continuously stirred tank reactor
**DM**: Dairy manure
**FW**: Food waste
**GM**: Goat manure
**GS**: Grass silage
**IRRI**: International Rice Research Institute
**KW**: Kitchen waste
**LD**: Liquid digestate
**LG**: Lawn grass
**MN**: Macronutrients (N and P)
**MS**: Maize stover/straw
**MSa**: Maize silage
**MSS**: Municipal sewage sludge
**OFMSW**: Organic fraction of municipal solid waste
**OLR**: Organic loading rate
**PASBR**: Psychrophilic anaerobic sequencing batch reactor
**PM**: Pig manure
**PMS**: Paper mill sludge
**PS**: Pig slurry
**PSa**: Phragmites straw
**PWW**: Piggery wastewater
**RM**: Ruminal microbiota
**rpm**: Revvolutions per minute
**RR**: Recovery rate
**RS**: Rice straw
**RSG**: Roadside grass
**S/I**: Substrate-to-inoculum ratio
**SD**: Solid digestate
**SEM-EDS**: Scanning electron microscopy
**SHW**: Slaughterhouse waste
**SM**: Swine manure
**SS**: Sewage sludge
**TC**: Total carbon
**TE**: Trace elements
**HR**: Hydraulic retention time
**TKN**: Total Kjeldahl nitrogen
**TN**: Total nitrogen
**TS**: Total solids
**VFAs**: Volatile fatty acids
**VS**: Volatile solids
**WS**: Wheat straw