###### Abstract
A solution to reduce costs can be reducing the engine-out emissions directly through advanced combustion process like low-temperature combustion (LTC) strategies. These approaches are considered a promising way to improve the efficiency of CI engines while reducing NOx and PM emissions simultaneously. In LTC, the combustion temperature is kept below the soot-forming region, and the lower temperature allows one to avoid thermal NOx formation [5]. Several LTC concepts like homogenous charge compression ignition (HCCI) and premixed charge compression ignition (PCCI), among others, have been suggested to achieve overall lower engine-out emissions [6]. LTC in a diesel-fuelled engine requires the production of a lean premixed charge to ensure a long ignition delay (ID) to enhance the charge homogeneity. Several strategies can be used to delay ignition such as early injection timing or high rate of exhaust gas recirculation (EGR) [7] allowing a simultaneous near-zero NOx and PM emissions [8] at the cost of high levels of unburned HC and CO [9]. A strategic way to achieve this purpose is using alternative and cleaner fuels [10]. Among them, ethanol is considered to be one of the most promising alternative fuels in diesel engines, which can significantly contribute to the reduction of particulate emissions at the exhaust [11]. It can be produced by direct fermenting of sugars, including sugarcane, sugar beet, sorghum, whey and molasses with yeast, from lignocellulosic materials, including woody materials, straws, agricultural waste and crop residues and catalytic hydration of ethylene [12]. Recently the ethanol production from microalgae gains attention due to their easy process to be converted in monosaccharides for biofuels production, to their high growth rate and short harvesting cycle [13]. For the aforementioned reasons, ethanol can be considered as a biofuel. The Kyoto protocol treats biofuels as carbon neutral because CO\({}_{2}\) emission for biofuel combustion is balanced out by absorbed CO\({}_{2}\) during the growth of the plants for its production [14]. In addition, the ethanol production from microalgae can be integrated into a circular sustainable process to generate clean water and energy reaching CO\({}_{2}\) fixation, and oxygen release [15]. There are several techniques involving ethanol-diesel in dual-fuel (DF) operation, and each concept comes with its upsides and downsides [16]. The simplest method is to add ethanol to the conventional diesel fuel and injecting the blend directly into the cylinder through the conventional diesel injector. The alcohol-diesel blends help to reduce engine emissions without significant impacts on engine performance. The main disadvantage is that the fuel substitution ratio (FSR) cannot be changed instantaneously and the ethanol fraction is limited due to its poor ignitibility and miscibility (this can be partly alleviated by emulsifying the mixture) [17]. Due to its low cetane rating (\(<\)10), ethanol also represents an interesting solution to be used as injected fuel via port fuel injection (PFI). When injecting the diesel and alcohol fuel separately into the cylinder, the substitution ratio can be changed faster than the previous case, and more diesel can be substituted with alcohol fuel than the blend case [18]. The main technical issue related to this concept is the use of two separate injectors leading to a more complex hardware and electronic systems conversion; nevertheless, the engine intake is generally easily accessible. This DF concept poses an upper limit for fuels substitution ratio due to knocking and ringing issues associated with a higher degree of premixed combustion in combination with a high compression ratio typical of a diesel engine [19]. In [20], the authors summarized a significant quantity of literature related to the alcohol fumigation concept in the dual-fuel combustion mode.