عنوان مقاله [English]
Rapid industrialization, demographic changes, improving human living standards, and growing populations are the main drivers of increasing energy demand [1, 2]. Dwindling fossil fuel reserves and growing concerns about increasing greenhouse gases have necessitated the exploration of alternative sustainable fuels to meet the growing order in the transportation sector and mitigate global warming and climate change. Among the environmentally friendly fuels that have been developed to date, fatty acid methyl or ethyl ester (biodiesel) obtained from vegetable oils, animal fats, and waste oils, which are considered due to their similarities in physiochemical properties to petrodiesel fuels. have been noticed [3-5]. Regardless of the renewable, carbon-neutrality, and biodegradability of biomass-derived fuels such as biodiesel , its use in pure or mixed form can significantly reduce the emission of toxic pollutants .
Although considerable progress has been made in producing Biodiesel from different raw materials. Its impact on the price of edible vegetable oils and the high cost of the product obtained using these sources has pushed the biodiesel industry towards the use of low-cost raw materials derived from leads to waste [8, 9]. Also, due to the different stages in the production of raw materials, biodiesel production, and product supply stages, each production path's environmental effects have differences [10, 11].
Due to the variety of raw materials and the different methods of biodiesel production, it is felt necessary to research and study to evaluate the cheap and more environmentally friendly production path to provide the most optimal product to replace fossil fuels.
This study aims to evaluate the biodiesel cycle obtained from waste oil, algae oil, and microalgae to investigate its environmental and economic effects.
several review papers analyzed biodiesel production from algae and other resources from the viewpoint of life cycle assessment. No systematic design study in the literature evaluates biodiesel production from algae regarding life cycle performance and taxonomy. This weakness can be considered a primary deficiency in this specialized field because there is no basic mapping for the desired aim. We decided to cover this weakness by doing a systematic review. We applied the PRISMA guidelines to investigate and assess the biodiesel production scenarios. The research was conducted in three stages. The first step is to collect the database, then analyze that data, and the final step is to report the study's primary findings.
To the best of our knowledge, the present study is one of the pioneer systematic reviews for evaluating biodiesel production from algae from the environmental point of view. Preparing periodic review papers on a particular scientific subject might consider and recommend policy changes. Several survey studies have recently been conducted to evaluate the role of life cycle assessment in biodiesel production from algae.
The present study employs PRISMA guidelines for the dataset-collecting process [22, 23]. PRISMA guidelines are responsible for locating and organizing records (Figure 1, Phase I). The Thomson Reuters Web-of-Science (WoS) and the Elsevier Scopus databases contributed 1105 of the papers, while the remaining 135 came from external sources. The screening looked for instances of duplication as well as specific cases (Figure 1, Phase II).
115 records were eliminated due to duplicates. The analysis of the titles and abstracts excluded 75 records. Phase III, which determined eligibility, chose 160 papers. The authors researched the selected records during the election monitoring process and picked the most pertinent samples. There was a censoring of the documents. As a direct result of this, 890 papers were looked into.
The results of various research in the field of evaluation of the biodiesel cycle obtained from algae oil, microalgae and waste oil were described. In converting microalgae into biofuel, paying attention to the comparative assessment of the life cycle can introduce the most appropriate product regarding environmental compatibility. In this context, biobutanol is more environmentally friendly than biodiesel . If supplied from inappropriate sources, especially fossil sources, the electrical energy used in the WCO biodiesel production process dramatically impacts human health and climate change. The production of Biodiesel from WCO by removing or reducing waste disposal can play an influential role in preventing and reducing water pollution by eliminating wastewater containing WCO.
Saranya et al. performed a comparative evaluation for microalgae cultivation considering different nutrient inputs, no nutrient input (scenario 1), wastewater as nutrient input (scenario 2), and fertilizer input (scenario 3). Acid catalyst and biocatalysts were used to convert microalgae oil into Biodiesel. The scenarios' environmental impacts were evaluated using OpenLCA v1.10.3, which highlights the further release of eutrophication and photochemical oxidation related to the fertilizer input scenario with acid catalyst transesterification .
To reduce the environmental impact, it is essential to pay attention to the WCO collection stage; Because the collection efficiency and the collection system's characteristics have the most significant impact. The energy spent on collection should lead to a suitable collection efficiency. In this regard, it is essential to pay attention to the type of system and population density of the region from which WCO is collected.
The present study investigated the impact of the life cycle assessment method on the production of Biodiesel from algae compared to other biomass. The results showed that:
- The production of microalgae biodiesel using wastewater and biocatalyst significantly reduces environmental effects.
- The production system of biofuels from microalgae requires a high investment, which includes 47-86% of the total production costs.
- WCO biodiesel produces less CO2 compared to first-generation Biodiesel. The added value of WCO is preventing water pollution through its release.
- Using eggshell CaO biocatalyst in WCO biodiesel production shows better environmental effects than KOH alkaline catalyst.
In the WCO life cycle assessment, the waste collection stage and the details of this stage should also be considered.
Paying attention to the stage of waste oil collection in the evaluation of the life cycle of the resulting Biodiesel will lead to the recognition and correct decision regarding its environmental effects; Therefore, it is appropriate to pay more attention to this issue in future studies.
The production of Biodiesel from microalgae oil has the problem of high initial investment to establish a cultivation site, extract oil from it, and convert it into Biodiesel; Therefore, it will be appropriate to pay more attention to the reduction of these costs in future studies.