Biochar is a versatile material with various applications, such as soil enhancement and energy generation. Additionally, it is renowned for its capability to adsorb waterborne contaminants. Nevertheless, the utilization of untreated biochar for this purpose falls short due to its typically constrained adsorption capacity. Consequently, chemical modification of biochar can be employed to enhance its adsorption properties and optimize adsorption efficiency, leading to the development of an ‘engineered biochar’ that is more effective in water treatment. Although numerous studies have been carried out on engineered biochar in the past decade, there has been limited exploration into their environmental impacts and the assessment of their life cycle, both in terms of assessment (LCA) and cost (LCCA). In this study, we investigated the LCA and LCCA of canola straw biochar modified using H3PO4 and FeCl3 developed for the adsorption of arsenic. LCA analysis showed that the biochar composite production process generates 0.134 kg CO2 eq per kg of biochar, while LCCA results displayed an overall price of $6.95 USD per kg of biochar. Additionally, we examined a weighting scenario to compare the LCA and LCCA outcomes of the biochar composite produced through conventional pyrolysis with those of microwave pyrolysis. This evaluation led to the recommendation of microwave pyrolysis over conventional pyrolysis. In summary, this study contributes to a deeper understanding of the practical environmental and economic implications associated with the utilization of biochar as an adsorbent.