The conversion of oil palm waste to valuable fuels via biological and thermochemical means has witnessed much interest from researchers. Increasing tonnes of palm waste resulting from about 400 palm oil mills across Malaysia necessitates a rethink towards its conversion to energy to curb soil and air pollution, underground water contamination, and pest habitats. Converting these palm wastes to fuel at a commercial scale is necessary to advance Malaysia's bioenergy. This will ensure cleaner production and sustainability by providing low carbon energy that could be used in industrial, transport, and residential sectors. However, what is the technology readiness levels of these conversion methods in Malaysia? Have they reached commercialisation? What hinders them from attaining it? This study conducted an intensive literature review on five conversion technologies broadly classified as thermochemical (combustion, gasification and pyrolysis) and biological (anaerobic digestion and fermentation) to identify the extent to which each process has been adopted. For each of the technologies, the following were established: (1) Studies conducted by researchers using different palm wastes; (2) Challenges faced; (3) Technology readiness level. The significant findings revealed that fermentation is still at a lab scale, gasification and anaerobic digestion have reached pilot-scale while combustion and pyrolysis have attained commercialisation. Significant commercialisation challenges include technical and economic issues, communal consciousness, and stakeholder gap. Current research gaps, recommendations, future outlooks, and the way forward were discussed, along with developing a framework that features the key barriers, enablers, and stakeholders responsible for commercialisation.

Graphical Abstract

The conversion of palm-oil biomass to renewable energy fuel has been achieved majorly using two ways, biological means and thermochemical means. The biological conversion is based on the activities of microorganisms under certain conditions. The thermochemical conversion involves the introduction of heat to the biomass. In combination with the medium, the intensity of the heat applied to the medium, reaction parameters, and reactor type determines the final products. Fig. 4 illustrates the pathways for biomass conversion. The thermochemical conversion is majorly categorized into three, i.e., gasification/co-gasification, combustion/co-combustion, and pyrolysis/co-pyrolysis. These processes may either be catalytic or non-catalytic. The biological means applied to the palm-oil waste are predominantly fermentation and anaerobic digestion.

Emergence and advancement of renewable energy policies in Malaysia

Resource Optimization: Oil palm waste is abundant in Malaysia due to its prominent palm oil industry. By converting this waste into energy, it optimizes the utilization of resources that would otherwise be discarded or underutilized.

Reduced Environmental Impact: Converting oil palm waste into energy helps mitigate environmental issues associated with its disposal, such as air and water pollution from burning and landfilling. It contributes to reducing greenhouse gas emissions, thus addressing climate change concerns.

Energy Security: Diversifying energy sources through the conversion of oil palm waste contributes to energy security by reducing dependence on fossil fuels. It can also potentially reduce the country's reliance on imported energy sources, enhancing economic stability.

Economic Opportunities: Commercialization of waste-to-energy technologies creates economic opportunities through job creation, investment in infrastructure, and the development of a renewable energy sector. It can also generate revenue streams for farmers and palm oil producers through the sale of waste materials.

Palm-oil biomass conversion pathway

Renewable Energy Demand: With increasing global awareness of climate change and the need to transition to renewable energy sources, there is a growing demand for sustainable energy solutions. Oil palm waste conversion methods offer a renewable and environmentally friendly energy source that can help meet this demand.

Abundant Feedstock: Malaysia is one of the world's largest producers of palm oil, generating significant amounts of waste biomass in the form of empty fruit bunches, palm kernel shells, and palm oil mill effluent. This abundant feedstock provides a reliable and readily available resource for energy production.

Government Support: The Malaysian government has shown commitment to promoting renewable energy development through various policies, incentives, and targets. Supportive regulatory frameworks and incentives, such as feed-in tariffs and tax incentives, can incentivize investment in oil palm waste conversion projects.

Energy Security: Diversifying Malaysia's energy mix with locally sourced renewable energy sources, such as oil palm waste, can enhance energy security by reducing reliance on imported fossil fuels. This can contribute to greater energy independence and resilience against global energy price fluctuations.

Proximate analysis of the palm-oil waste