ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Optimization of the compost C/N ratio in garden waste in-vessel composting using a machine learning

Dayanand Sharma, Hrishikesh Shivam, Saurabh Kumar, Divesh Ranjan Kumar, and Warit Wipulanusat

Civil Engineering Department, Sharda University, Greater Noida, India

E-mail: wwarit@engr.tu.ac.th

Received: 5 November 2025  Accepted: 19 January 2026

Abstract:

Quick urbanization leads to more garden waste generation and poses disposal challenges for municipalities. To solve this problem, reactors in which the temperature is regulated and the air is controlled, called controlled in-vessel composters, have been designed for effective composting. Three experiments were carried out using various garden waste forms grinded (T1), unshredded (T2) and shredded (T3) in a portable, temperature-controlled in-vessel reactor over an experimental period of 30 days. The temperature was maintained at 50–60 °C, and the moisture level was 65%. The monitoring results revealed considerable variations in the following composting parameters: cellulose content (from 42 to 3.5%), hemicellulose content (10–0.5%), lignin content (13–1%), total organic carbon content (40–37.6%), total nitrogen  ratio (4–0.6%), C/N ratio (from 61.5 to 34.2%) and pH (from 7 to 8%). These differences were used to optimize the C/N ratio with a multivariate adaptive regression splines (MARS) model. The MARS model achieved highly accurate predictions in  all trials, with R² values close to 1 for both the training and testing stages. This study revealed that different compost types play specific roles. Shredded compost provides rapid nutrient release for fast-growing crops. Ground compost helps maintain long-term soil health. Unshredded compost supports continuous mineralization and organic matter buildup. Integral assessment revealed that controlled in-vessel composting could accelerate decomposition  and reduce environmental impact and resource utilization, leading to a circular economy.

Keywords: Garden waste; Composting; Thermophilic; Nutrients; MARS

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-026-04685-w

Chemical Papers 80 (4) 4213–4229 (2026)