## 2 Method
### Conceptual Process  
The conceptual process is schematically presented in Figure 1. This concept is suggested to produce syngas in small methanol plants. Wood pellets are suggested as feedstock for the process. Raw syngas from wood contains less nitrogen oxides (NOx) and sulphur dioxide (SO\({}_{2}\)) than fossil fuels, making this syngas more suitable than these fossil fuels for fuel refining. Pellets can easily be produced nearby as a local bioresource and then transported to a small plant. Wood pellets represent a choice feedstock, being homogeneous (or quasi-homogeneous) in terms of composition, sizing, dryness, and ash and impurity content. The system capacity, or mass flow of ash-free, dry biomass feed, is set at 1000 kg/h. As shown in Figure 1, biomass is fed into a gasifier to produce syngas. The updraft fixed bed configuration was chosen as a convenient technology. The working principles of the updraft gasifier are illustrated in Figure 2. In the reactor, gasifying agent air or O\({}_{2}\) is inserted at the bottom and flows upward to generate producer gas. At the same time, biomass in the form of wood pellets is inserted at the top and moves downward through zones in which drying, pyrolysis, gasification, and oxidation occur stepwise. The temperature increases roughly from 200 \({}^{\circ}\)C in the drying area to 1000 \({}^{\circ}\)C in the oxidation area. This type of gasifier is selected because it offers key advantages for the intended application. The design and operation are simple. The producer gas from this gasifier contains light gases such as CO, H\({}_{2}\), CO\({}_{2}\), H\({}_{2}\)O, and methane (CH\({}_{4}\)), and tars that are in large part oxygenated, containing molecules such as anisole (C\({}_{7}\)H\({}_{8}\)O) [7; 8; 9]. These tars are easily thermally converted into simple molecules such as H\({}_{2}\) and CO. Complete conversion of oxygenated tars from updraft gasifiers was demonstrated [10]. In a downdraft gasifier, on the other hand, tars are made practically entirely of non-oxygenated molecules, such as aromatics such as benzene (C\({}_{6}\)H\({}_{6}\)) [11]. The latter do not convert as readily into simpler gaseous molecules. They require adding a considerable amount of steam to decrease cooking on surfaces downstream. The system energy efficiency is then reduced because of the heat required to generate and heat up steam, in addition to the highly endothermal nature of the steam reforming reaction. For example, these non-oxygenated tars can lead to cooking of the catalyst for methanol synthesis, thus reducing its activity. Residual aromatics such as benzene and toluene also represent a human health hazard. Fluidsied bed gasifiers generate a mix of oxygenated and non-oxygenated tars, bringing still similar issues as with the downdraft configuration [12]. Figure 1: Schematic block diagram of a conceptual integration of water electrolysis with biomass gasification. When dealing with small plants, fluidised bed gasifiers also have higher manufacturing costs, and are trickier to operate and maintain, compared to fixed bed gasifiers. The fact that oxygenated tars from the updraft gasifier react easily precludes the need of adding large quantities of steam or separating these tars for disposal. The energy content of these tars is then preserved in the syngas as sensible heat or heating value of tar decomposition products. The process carbon yield is kept higher as a result. Updraft gasifiers are also known for their durability. A commercial unit fueled with wood chips was operated for more than 120,000 h [13]. Even though tars generated in the updraft gasifier react at a lower temperature compared to tars from other gasifiers, they exit the reactor in a zone that is too cold for them to react. The raw syngas needs to be heated up to a higher temperature after exiting the conventional reactor area, meaning after passing through the drying zone.