1. Introduction
In recent decades, the production and use of plastic has significantly increased, resulting in a concerning increase in plastic waste. The situation has prompted initiatives to tackle this issue; however, a substantial amount of the aforementioned waste is present in aquatic areas, ranging from large plastic fragments to microplastics [
1]. A notable issue arises with river pollution as plastic items do not only pollute the water but also worsen flooding potential by obstructing drainage systems [
2]. This pollution greatly affects ecosystems and poses a threat to the diversity of plant and animal life.
Currently prevalent pollutants consist of microplastics. These are fragments that are smaller than 5 mm in diameter [
3]. These minuscule particles infiltrate freshwater and marine environments and adversely affect organisms by becoming part of the food chain. It is anticipated that by the year 2040 the amount of waste polluting the oceans annually will triple to reach a total of 37 million tons [
4].
Projections suggest that without intervention in waste management practices, by 2050, when global plastic waste is expected to reach 1 billion tons, humanity will be facing a volume of waste that exceeds the planets capacity to cope [
5]. Given the gravity of the situation, humans are confronted with the task of developing waste disposal regulation solutions that are urgently needed [
4]. Governments must collaborate with industries and individuals to enforce policies aimed at reducing plastic production and enhancing recycling efficiency while advocating for alternatives to single use plastics. Failing to act could result in environmental repercussions that may ultimately jeopardize ecosystems and human health in the long run.
Recycling is a commonly suggested manner of repurposing waste and mitigating its harm; nevertheless, it is not devoid of downsides, like the energy requirement and resources that could harm the environment instead of helping it thrive. In addition, it is not always economically viable to recycle mixed plastics. Other waste management methods, like pyrolysis, may offer solutions to these issues [
6].
Pyrolysis and other related techniques, like liquefaction and gasification, have the ability to convert waste into fuels and chemicals while also producing energy [
7]. These chemical processes neither greatly diminish landfill waste nor eliminate environmental impact, but they are known for their high material recovery rates. By incorporating these methods, industries can embrace circular economic approaches that enhance resource efficiency and prolong the lifespan of plastic goods.
The advantages of pyrolysis technology become evident when compared to gasification and liquefaction methods because it provides better performance for decentralized and small-scale applications [
8]. The gasification process operates at elevated temperatures to produce syngases which require extensive purification before utilization [
9]. The production of high-quality fuels through liquefaction requires high pressure and catalysts which increase operational complexity and cost [
10]. The process of pyrolysis operates at moderate temperatures without oxygen and handles mixed plastic waste through basic reactor designs, which makes it suitable for modular industry-integrated systems [
11]. In recent years, the progress that has been made in chemical recycling methods has greatly improved their effectiveness and ability to be scaled up [
12]. These innovations play a significant role in dealing with the increasing plastic waste issue. Pyrolysis projects in areas such as Asia, Australia, and America are gaining popularity as they demonstrate a process that extracts energy from discarded materials [
13,
14]. These projects are not only aiding in the minimization of waste but also laying the groundwork for ecofriendly energy options by transforming waste into valuable fuels and chemicals.
Significant upfront expenses and infrastructure constraints, along with the need to maintain energy efficiency in large-scale operations, remain obstacles to overcome in adopting technologies today, despite these challenges indicating a positive step towards a circular economy [
15]. Combining chemical recycling with waste management approaches has the potential to cut down significantly on waste while also producing renewable energy as a byproduct. This shift not only improves environmental sustainability but also creates economic advantages by opening new opportunities in recycled materials and alternative fuels markets. Further investigation and funding are required to overcome the obstacles hindering the adoption of these innovative solutions in various fields of study or application areas. While centralized systems are typically chosen for implementation purposes due to their convenience and efficiency features, their installation demands investment in large scale facilities and an extensive waste management infrastructure that is costly and lacks long-term environmental sustainability [
16]. The process of transporting waste to processing facilities is intricate and results in greenhouse gas emissions. Moreover, establishing and maintaining pyrolysis facilities necessitates resources, making it challenging to implement in regions where the residential waste collection system is ineffective.
Although pyrolysis provides advantages for waste management, centralized systems may not be as sustainable for expanding operations. On the contrary, decentralized waste-to-energy systems have shown promising results in cost reduction and reduced environmental impact [
17].
These more compact systems could provide flexibility and effectiveness for managing localized waste. Additionally, they could lower transportation expenses and environmental harm, making them an area worth exploring further. These systems seem to offer the opportunity for businesses to transform their waste into energy to run their activities as well as supply electricity to relevant companies and earn additional revenue using valuable federal protocols like net metering [
18]. Nonetheless there is still a lack of in-depth investigation into customized solutions designed specifically for managing waste within different industries while also capitalizing on potential secondary revenue streams from these materials [
19].
The literature contains similar initiatives. Uzosike et al. [
3] investigated small-scale mechanical recycling systems and Vasileiadou and Tsioptsias [
4] studied the combustion kinetics of plastic–lignite blends. Rathi et al. [
6] studied the catalytic conversion of plastic waste into fuels. Certain pieces of research [
6,
7,
13,
20] have investigated centralized pyrolysis systems and their implementation in national energy policies. The majority of existing research investigates either large-scale facilities or theoretical models exclusively [
5]. This research presents a complete operational framework for a decentralized pyrolysis-CHP (Combined Heat and Power) unit designed for SMEs (Small and Medium-sized Enterprises) that incorporates actual techno-economic data and modular system design.
This study introduces a new approach through its techno-economic assessment of a decentralized small-scale pyrolysis system which targets SMEs that generate substantial plastic waste. The proposed system differs from previous research because it presents a modular solution which enables on-site energy recovery while reducing costs through Combined Heat and Power (CHP) integration. The system includes standard industrial components alongside detailed operational modelling and net metering potential, which previous studies have not fully explored. The approach represents a groundbreaking method to achieve localized industrial energy independence.
Previous research has introduced decentralized and mobile pyrolysis units, yet most of these systems lack complete CHP integration and do not present complete technical and economic implementation models [
21]. This system transforms plastic waste into synthetic pyrolysis diesel-type fuel at the site while offering modular expansion capabilities and net metering functionality and complete breakdowns of mechanical parts and expenses. The complete and ready-to-implement design distinguishes this decentralized solution from others in the field. It emphasizes the concept of energy circularity by lowering the engine’s temperature and supplying thermal energy [
22]. This model is especially well suited for companies that produce huge quantities of waste, like plastic film manufacturing [
23]. Additionally, this method decreases reliance on external waste management services and reduces energy expenses, which makes it a feasible and environmentally friendly option.
4. Discussion
The proposed unit works at full capacity for 66% of the time and processes plastic waste for 8 h each day from mid-October to mid-April. It produces 500 MWel and 60 MWhth, with the discharged thermal energy being utilized for heating purposes. The energy potential of plastic waste is about 40,000 kJ/kg, and 675 kg of plastic waste is processed; thus, 80% energy recapture is achieved. Also, the thermal energy output of the diesel engine, i.e., 60 MWhth, is used to substitute fossil diesel with an energy composition of 11.75 kWh/kg and combustion competence of 0.85, which results in annual savings of 5100 kg of heating oil. The entire equipment’s value is EUR 35,000, with an operational power cost of EUR 770/year. The initial cost of establishing a pilot plant unit is approximately EUR 60,000. Running for 8000 h/year, the unit produces ~160 tons of synthetic pyrolysis oil, which provides energy equivalent to 123 tons of diesel obtained from fossil sources. The produced electrical energy provides energy demand to small-scale industries but also generates power which can be fed back to the grid. Furthermore, the system is environmentally friendly in the sense that it helps with waste management and promotes the use of energy from renewable sources. The economic benefits and environmental advantage make it attractive to invest in this project. The proposed system demonstrates promising techno-economic potential, yet multiple technical limitations need evaluation. The quality of synthetic pyrolysis oil produced by pyrolysis depends on feedstock composition, which demands pre-treatment or blending to achieve engine compatibility. The maintenance expenses will increase with time because of reactor and oil pipeline residue accumulation when feedstock sorting is inadequate [
60]. The operational stability of CHP units requires periodic calibration and durable components, especially for small-enterprise modular installations [
61]. The assessment of durability and system design optimization for industrial deployment requires pilot testing because of these factors. This way of thinking minimizes energy loss and reduces carbon emissions significantly, in line with sustainability targets.
The technical specifications and design requirements of the proposed Waste-to-Energy (WtE) technological solution intends to address two major problems: (1) management of non-reusable and non-recyclable plastic waste streams; (2) production of substantial energy to match growing requirements in various areas of the world. One of the most important problems of the present day is the effect of waste on the environment; the waste sector has to shift to an ‘intelligent’ supply chain. As an example, this paper has argued that, by emphasizing the role of different industries in environmental degradation and climate change, it is possible to encourage the adoption of measures that can mitigate these effects [
49]. However, this approach presents a way to a profitable, sustainable path towards decarbonizing industries. A solution that is both cost-effective and effective is offered. In fact, this innovative energy solution may very likely be taken up first by smaller businesses that are particularly prone to adopting new technologies. This technology solves the main issue of plastic waste management through chemical processes that are similar to those employed in the processing of biomass. It is regarded as an environmentally friendly system since waste management is combined with the future plan to make industries carbon neutral. Waste to fuel is a beautiful and sustainable way of recycling natural resources.
EU Waste Framework Directive (2008/98/EC) and Renewable Energy Directive (2018/2001/EU) establish regulatory requirements for decentralized pyrolysis system deployment. Waste-to-energy solutions receive EU support when waste prevention and recycling maintain their priority status [
62]. The Greek government regulates waste incineration activities through national transpositions of EU law which focus on emissions and environmental permitting (Joint Ministerial Decisions 22912/1117/2005 and 37411/2031/2003). The legal classification of pyrolysis as a recovery operation instead of waste incineration could simplify licensing procedures. This distinction enables SMEs to establish decentralized units through flexible permitting pathways [
63].
The proposed system can integrate renewable energy sources through biomass feedstock to decrease initial heating requirements and minimize carbon emissions. Real-time monitoring of reactor parameters becomes possible through IoT-based control systems which enables digital monitoring for small-scale applications to achieve better efficiency and reliability.