## 1 Introduction  
Tars formed during biomass gasification are an important problem for installations located downstream of the gasification reactor. They cause clogging of pipes and valves and damage to engine and turbine components. For that reason, there are limits recommended separately for various applications such as \(<\)100 mg/m\({}^{3}\), \(<\)5 mg/m\({}^{3}\), and \(<\)1 mg/m\({}^{3}\) for internal combustion engines, gas turbines and fuel cells, respectively [1]. This means that the concentration of tars must be drastically reduced before application since their amount in the biomass producer gas is typically in the range of 1-150 g/m\({}^{3}\)[2].  
There are many methods to purify gas of tars [1; 2; 3]. Among the methods, the most attractive are those that enable the transformation of undesirable tars into components that increase its energy and chemical value. These include catalytic cracking and hydrocracking of light hydrocarbon tars, dry or steam reforming of tars into carbon monoxide and hydrogen, thermal cracking, leaching in suitable solvents, and plasma methods.  
The plasma used to purify the gas from biomass gasification is generated by various types of electrical discharges. Its advantage is instant high gas temperature and high reactivity due to the presence of energetic electrons, ions, and radicals. The largest amount of research is related to arc, dielectric barrier, corona and microwave discharges and their combinations with catalytic materials [4; 5; 6; 7; 8; 9; 10; 11; 12; 13; 14; 15; 16; 17]. An excellent review of the application of plasma-cataly systems for tar removal was presented in [18] and most recent [19].  
In this work, a dielectric barrier discharge (DBD) reactor combined with catalytic materials was used. DBD reactors are considered to be very attractive for heavy hydrocarbon cracking due to the high electron density and energy, plasma homogeneity, simple design and operation, capacity to induce reactions at relatively ambient temperature, atmospheric operational pressure, and very low level of coke production [20]. The novelty of this work lies in the combination of four problems that have so far been studied independently or in a smaller combination, i.e.,:  
1. Number of gaseous components entering a reactor--similar to a real biomass producer gas, which was considered only in [9; 21];
2. Number of tar components--in this work 3 tar representatives were used together while in most cases only 1 or 2 are used [11; 15; 16; 22; 23; 24; 25; 26; 27; 28; 29; 30; 31; 32; 33; 34]. Excluding a few works performed on real biomass producer gas [9; 14; 21] only [PERSON] et al. [17], [PERSON] et al. [10], [PERSON] et al. [12] and [PERSON] et al. [35] used at least 3 tar components, but in nitrogen, argon and oxygen as a plasma-forming gas;
3. DBD plasma with a catalyst--this has been studied by many researchers [18] and is called a one-stage configuration since the catalytic material is in contact with the plasma. The advantage of this configuration is the use of radicals, which are formed in the plasma and which have a very short lifetime;
4. Nanosecond high-voltage pulses--investigations have shown that shortening high-voltage pulse leads to increasing the formation of highly energetic electrons, ions, radicals and exited molecules at the same input power [36]. Such short pulses were used for tar removal only by researchers from Eindhoven University of Technology in pulsed corona discharge reactors [4; 5; 6; 7].