Pyrolysis is considered as a sustainable way to generate energy from bio-oil, however, biochar – a solid residue by-product– is inevitably produced in the production line. We have previously attempted to modify biochar as a solid acid catalyst with magnetic functionality. The material showed promising catalytic activity for the esterification of oleic acid and methanol to give a 64% yield of FAME (biodiesel). In order to optimise their catalytic performance, a deeper understanding of the surface properties of biochar is essential. INS is ideally suited for the investigation of carbon-rich amorphous materials. We would like to understand the surface chemistry and details of the interaction between the catalyst and the oleic acid adsorbate. The use of biochar as a low cost and renewable carbon based solid acid catalyst will open new applications in industrial catalysis.