Assessing the implementation levels of oil palm waste conversion methods in Malaysia and the challenges of commercialisation: Towards sustainable energy production

Highlights

• Malaysian oil palm wastes have the potential to improve the share of bioenergy in the country's energy mix.

• Fermentation of the palm waste is at lab scale.

• Gasification and anaerobic digestion of palm waste has reached pilot scale.

• Combustion and pyrolysis have attained commercialisation.

• Commercialisation is possible through factors such as proper logistics, technology, human capital and workable policies.

Abstract

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.

Introduction

Biomass wastes have colossal energy potential as renewable energy resources, and conversion of such wastes solves environmental problems and energy demands, thus leading to sustainability and cleaner production. Oil palm wastes are lignocellulosic biomass made up of primarily lignin, cellulose, and hemicellulose constituents. Oil palm waste happens to be the most abundant biomass waste in Malaysia. However, this biomass waste has been underutilized, limited to landfills and soil amendment purposes. However, palm waste can be converted to numerous sources of clean energy and end products, which do not add carbon to the atmosphere. Obtaining clean energy and end products can be achieved through thermochemical and biological conversion methods [1]. Biomass thermochemical conversions involve using heat to transform the biomass into value-added fuels through majorly gasification, pyrolysis, and combustion. On the other hand, biological conversion occurs naturally through the use of bacteria, microorganism, and enzymes to produce green fuels through fermentation and anaerobic digestion. Thus subjecting the oil palm waste through sustainable methods (thermochemical and biological) to yield green fuels such as syngas, bio-oil, biochar, biogas, and ethanol will ensure a cleaner environment and energy, thus ensuring sustainable development and cleaner production.

Malaysia is the world's second-largest producer of palm oil, as depicted in Fig. 1. Its massive palm oil import is based on its vast oil-palm plantation of about 5.4 million hectares, which generates about 90% of lignocellulosic biomass waste in Malaysia [2]. Palm oil processing companies produce several types of wastes when a tonne of fresh fruit bunch (FFB) is processed. These wastes include empty fruit bunch (EFB) (23%), mesocarp fiber (MF) (12%), palm kernel shell (PKS) (5%), and palm oil mill effluent (POME) (60%). Apart from the mentioned mill wastes, there is also the oil palm frond (OPF), and oil palm trunk (OPT) obtained from the plantation [3]. EFB is obtained when the fresh palm fruits are removed from the fibre-like bag that holds them together. It is a hairy fibrous biomass. MF is the leftover fibrous remaining obtained when oil is extracted from the palm fruits. The PKS is the hard black shell residue left after the nut is removed during fruit crushing in the mill. The OPT is obtained when the palm tree is felled down, while the OPF is the palm tree branches obtained during replanting and pruning periods. In 2018, the planted area was reported by the Malaysian palm oil board (MPOB) as 5,849,330 ha with a large replanted area and a considerable amount of (million tonnes) of freshly harvested fruits that were processed in 400 mills across Malaysia [4]. This vast process generated varying amounts of biomass based on standard extraction rate [[5], [6], [7]], as shown in Table 1. In addition, other waste also obtained via the replanting process include OPT and OPF. The total amount of palm-oil-based biomass waste obtained from milling, pruning, and replanting activities added up to 49.16 Mt (dwb) in 2018 [8].

Among the palm-oil biomass, only mesocarp fibers (MF) and palm kernel shell (PKS) are being utilized on a large scale in processing mills as boiler feed for cogeneration of heat and power (CHP) systems. Thus commercial utilization of palm-oil waste will provide a huge opportunity to launch it as a renewable energy enterpriser. If it is properly adapted, it will decrease the country's dependency on fossil fuel for energy [2].

The expansion in palm-oil plantation activities resulted in soaring rates of produced waste quantities during the replanting and fruit harvesting periods. During the annual harvesting of FFB, about 24% of OPF is accounted for from each palm-oil tree, while OPT obtained during replanting reaches up to 70% [10]. This translates to increased availability potential of both palm waste (OPT and OPF) throughout the year. Apart from the two palm wastes, other types like EFB, PKS, and waste POME are continuously provided as wastes by the numerous palm-oil mills running across the country [11]. Fig. 2 illustrates the generation of palm oil waste in the palm-oil cycling process in which OPT and OPF were obtained at the plantation site, whereas the EFB, PKS, MF, and POME were obtained after the fresh fruit processing.

As a result of the prohibition of harmful palm waste disposal methods, mill operators abandon the waste at their sites, which results in water and environmental pollution. The area becomes a harbour for pests, generates terrible odour, and adds toxic chemicals to the soil. In a search to handle the ecological challenges resulting from palm waste, scientists have been entrusted and dedicated to investigating ways to convert the abundant palm wastes into significant materials for possible applications in the industry [12]. This will ensure a cleaner environment, and at the same time, means of securing sustainable energy. The palm waste can generate green energy sequel to their physicochemical properties given by proximate and ultimate analysis shown in Fig. 6, Fig. 7. This energy that can be tapped and used instead of fossil fuel energy will help reduce the level of carbon released into the atmosphere. Thus achieving cleaner production, sustainability, and more revenue to the palm industry and the country. Other sectors that will benefit from the process include indigenous boiler manufactures, project developers, local energy service industries, energy consulting firms, financial institutions, and policymakers. Over the years, Malaysia has been striving to minimize its fossil fuel consumption to maximize its renewable energy utilization through its abundant palm biomass. This is necessary to enhance the sustainability of the energy supply and reduce the negative impacts of energy generation. It will also ensure control in the waste disposal and significantly recover green energy and high-value chemicals for commercial applications such as syngas. With this obligation, the country has since then improved renewable energy development by fostering joint efforts between government agencies and tertiary institutions to implement the technical and commercial aspects of its mission, including research and development of palm biomass wastes.

Palm waste has been utilized over the years for energy generation in Malaysian oil palm industries, especially in combustion processes to generate steam to process fresh fruits. However, there is a need to scale up the conversion processes to commercialisation levels to exploit palm waste's potential fully. The conversion processes deliver promising products like syngas from gasification, bio-oil/biochar from pyrolysis, Ethanol from fermentation, biogas from anaerobic digestion, and heat from combustion. These products can provide low-carbon energy suitable for use in the industrial, residential, and transport sectors. Additionally, this will pave the way for proper waste management and environmental sanitation, ensuring a steady supply of clean energy. The potential and utilization levels of these biomass wastes by adopting different conversion means in Malaysia are unknown. Hence, this paper intends to;

• Review the availability and potentials of oil palm waste in Malaysia

• Provide an overview relating to the current status and potentials of the two biomass conversion techniques that are applied in the country that is thermochemical (gasification, pyrolysis, and combustion) and biological (fermentation, and anaerobic digestion), showcasing the technology level of implementation of the various processes, that have been applied to the different oil palm wastes through past studies, and

• Identify challenges in the development and commercialisation of the conversion techniques

Malaysia is committed to developing its renewable energy sector through biomass conversion. It has led to launching projects like the bio-economy transformation program (BTP) to initiate biomass-based industries (2016). Similarly, the national biomass strategy (NBS) for biomass value-added goods (2020) was introduced (details of the renewable energy policies are discussed in Section 3). Hence, the present study is critical in providing the relevant stakeholders of such projects with vital information on the development levels of the biomass conversion technologies, the challenges that face them, and the areas that need improvement. Promoting the technologies to a commercialisation scale will go a long way in helping Malaysia achieve its goals to reduce greenhouse gas emissions, promote sustainable and low carbon energy. This will assist in tackling global climate issues and environmental challenges. The information will allow the stakeholders to strategize policies that will propel the commercialisation of the techniques. Those techniques in the lab-scale will be enhanced by more funding through grants to universities and research centers to improve advanced research and collaboration to reach pilot scale and eventually to commercialisation. The study also identified gaps and future research opportunities associated with conversion technologies.

Given the above, therefore, this review article seeks to address the following questions:

• What are the levels of technology of the conversion methods employed on palm-oil waste in Malaysia?

• What are the challenges facing the different conversion methods and hindrances to the commercialisation of these processes?

• What are the potential barrier breakers to reaching the commercialisation scale?

The literature review was carried out using various materials, including journal articles, conference papers, and internet sources. In addition, relevant articles were retrieved through Web of Science, Scopus, Science Direct, and Google Scholar. Some of the following keywords were used for the literature search “oil-palm waste,” “oil palm waste conversion,” “thermochemical conversion of palm waste,” “biological conversion of oil palm waste,” and “conversion of oil palm waste.”

The paper is structured as follows; Introduction was given in section 1. Section 2 discusses an overview of palm-oil plantation and palm waste potential in Malaysia. Next, the Malaysian government policies and capacity for renewable energy were discussed in Section 3. Section 4 gives a detailed review of the conversion techniques base on the; (i) the studies conducted on the individual palm wastes (OPT, OPF, PKS, MF, EFB, and POME) for the different conversion techniques (ii) Challenges and level of implementation. Section 5 gives the recommendation and way forward for commercialisation. Section 6 presents the summary/discussion. Lastly, section 7 presents the concluding part, emphasising the benefits of upgrading conversion systems to commercialisation.