**4. Conclusions**

Executed experiments, on the application of biochar produced from the same substrate as used for the anaerobic digestion (food waste) under different low-temperature and pressure conditions, indicated that:


Further research is needed at low-temperature biochars since this study did not clearly reveal the dependence between low-temperature biochars addition and methane production yield. More trials with different biochar production pressure variants, biochar doses, and at different food waste concentrations should be performed for the validity of the low-temperature biochar application in AD.

**Author Contributions:** Conceptualization, K.S., B.M., A.B.; methodology, K. ´ S.; software, K. ´ S.; vali- ´ dation, K.S. formal analysis, B.M, P.T., K. ´ S.; investigation, B.M.; resources, B.M.; data curation, K. ´ S.; ´ writing—original draft preparation, K.S. and B.M.; writing—review and editing, K. ´ S., B.M., A.B.; ´ visualization, K.S.; supervision, A.B.; project administration, K. ´ S. and A.B.; funding acquisition, B.M. ´ and A.B. All authors have read and agreed to the published version of the manuscript.

**Funding:** The research was financed under the individual student research project, Młode umysły—Young Minds Project" from the subsidy increased for the period 2020–2025 in the amount of 2% of the subsidy referred to Art. 387 (3) of the Law of 20 July 2018 on Higher Education and Science, obtained in 2019. The APC is financed by Wroclaw University of Environmental and Life Sciences.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** All data derived during the experiments are given in the paper.

**Conflicts of Interest:** The authors declare no conflict of interest and declare that the funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.

#### **Appendix A**

**Figure A1.** The biochar 400/60/15 production process, process parameters.
