The purpose of this thesis was to carry out a research on reuse possibility of surplus foundry sand in composting and develop a general proposal for guideline only as appendix in this thesis for the Finnish foundries to assist them in setting quality control system criteria to control the quality of surplus foundry sand suitable for composting and preventing any harm or risk to environment, human and natural resources. The research was made on the typical foundry sand used such as alkaline phenolic sand, furan sand and green sand that are used in Finnish foundries. The reuse possibility of surplus foundry sand was studied using various articles, journal published in this topic and also based on the experiment conducted by LIFE13 ENV/FI/285 “Foundry sand” project. The proposal to improve the waste quality of surplus foundry sand was prepared under environmental relevant industrial waste management activity (646/2011). Following conclusion can be drawn from the experiment conducted in three different Finnish foundries’ sand to find its reuse possibility in composting: the composting experiment showed that surplus foundry sand that would have been dumped in landfill contains fluoride, phenol and BTEX. These harmful components disappear during composting. This shows that reuse of surplus foundry sand does not adversely affect the environment. The proposal prepared for Finnish foundries in this thesis could be a reliable way to get clear and existing advice for them that would ensure and develop confidence about the consistency in quality of surplus foundry sand produced in foundries. It was found that there is a huge scope of applications for using surplus foundry sand.