Environment and Ecology Research 11(6): 973-978, 2023 http://www.hrpub.org DOI: 10.13189/eer.2023.110608 Utilisation of Ruminant Waste Microorganisms in a Simple Co-Composting Method in Bioremediation of Used Oil Contaminated Soil Ivone Wulandari Budiharto 1,* , Surya Kusuma Wijaya 2 , Dwi Budiono 2 , Citra Buana Sari 1 1 Environmental Engineering and Management Study Program, College of Vocational Studies IPB University, Indonesia 2 Veterinary Paramedic Study Program, College of Vocational Studies IPB University, Indonesia Received August 21, 2023; Revised October 27, 2023; Accepted November 20, 2023 Cite This Paper in the Following Citation Styles (a): [1] Ivone Wulandari Budiharto, Surya Kusuma Wijaya, Dwi Budiono, Citra Buana Sari , "Utilisation of Ruminant Waste Microorganisms in a Simple Co-Composting Method in Bioremediation of Used Oil Contaminated Soil," Environment and Ecology Research, Vol. 11, No. 6, pp. 973 - 978, 2023. DOI: 10.13189/eer.2023.110608. (b): Ivone Wulandari Budiharto, Surya Kusuma Wijaya, Dwi Budiono, Citra Buana Sari (2023). Utilisation of Ruminant Waste Microorganisms in a Simple Co-Composting Method in Bioremediation of Used Oil Contaminated Soil. Environment and Ecology Research, 11(6), 973 - 978. DOI: 10.13189/eer.2023.110608. Copyright©2023 by authors, all rights reserved. Authors agree that this article remains permanently open access under the terms of the Creative Commons Attribution License 4.0 International License Abstract The increase in vehicle ownership is directly proportional to the increase of lubricant oil usage (used oil) which has an impact on the environment. The purpose of the study was to determine the ability of the co-composting method to reduce the content of pollutants in soil contaminated with used oil by adding organic waste with ruminant livestock waste which contains many microorganisms. The used method for co-composting is a laboratory-scale rotary aerobic composter for 10 days of treatment with treatment components of 500ml used oil lubricant polluted soil, 1kg leaf litter, 2kg ruminant waste and 150ml agricultural EM4. The measured parameters were temperature, colour, texture, pH, humidity, Total Petroleum Hydrocarbon (TPH) and red spinach plants. The results showed that there were changes in the test parameters during the 10 days of treatment. The results of the T test data analysis showed that the application of compost fertilizer from the remediation results had a very significant effect on temperature, pH, humidity and a significant effect on the number of leaves due to the content of nitrogen (N) in compost that stimulates the formation of stems, roots and leaves. Isolated and identified microorganisms that consist of 14 bacterial isolates derived from ruminant livestock manure Application of microorganisms and EM4 bioactivator influenced the degradation of pollutants. The longer the composting process, the higher the percentage of TPH degradation. Keywords Composting, Contaminated Soil, Parameters 1. Introduction Currently, the automotive industry is growing very rapidly, characterised by the large number of motor vehicles. Increase in vehicle ownership is directly proportional to the increase in lubricant oil usage (used oil) (Azharuddin et al, 2020). The continuous utilisation of oil results in a massive amount of used oil waste ( Buana et al, 2021). Most components of petroleum waste contain total petroleum hydrocarbons (TPH) which are reactive, mutagenic and toxic, and are included in dangerous waste (B3 waste). TPH is a hydrophobic compound with low water solubility, making it easy to bind with toxic solid organic particles. These toxic substances accumulate in the environment, requiring human intervention and existing technology to resolve this pollution (Dewi et al, 2023). The basic concept of bioremediation is to recover all organic matter using the biological activity of microorganisms, nutrients, electron donors and acceptors, which contribute to the hydrocarbon degradation (Latif et