Socio-economic and environmental feasibility of the project

The biogas production in cases of SBO addition in the digester and without addition was evaluated with the CML-2001 (Jan 2016) methodology. According to the results, the environmental impact categories of the GWP, abiotic depletion of fossil and acidification potential instigates the same values (GWP = 0.51 kg CO₂-equiv per kg of biogas produced, abiotic depletion=0.83 MJ/kg biogas, acidification potential= 2.17 g SO₂-eq/kg biogas) gave the same values in the cases of biogas produced in the presence and in the absence of added SBO. This was expected due to the low amount of SBO added in the anaerobic fermentation slurry. For the prospected municipal biowaste biorefinery integrating biochemical fermentation and chemical hydrolysis processes, the results confirm three important SBO effects:

1. The major effect of the SBO assisted fermentation process is the decrease of eutrophication potential. This was replicated, although at different levels, for the three fermentation plants. It amounted to 27 %, 68 %, 25 % for the ACEA, OT, SBLA cases, respectively.
2. The environmental benefit expectations for the SBO assisted anaerobic fermentation are confirmed. This is clearly related to ammonia reduction in the anaerobic digestate, which amounted to 28 %, 67 %, 27 % for the ACEA, OT, and SBLA cases, respectively.

Social impact

1. As child labour is forbidden in the European Union, this indicator is considered zero for all selected biorefineries.

2. Regarding the subcategory fair salary, the indicators of living wage and minimum wage are evaluated by comparing the salary considered for the labour of project process to the living wage and minimum wage of the countries of EU-27 as well as to the average wages. As Figure 1 illustrates (ACEA case), the ratios of 24 out of 26 for the living wage and 18 out of 21 for the minimum wage are above 1, which means that the considered salary is above the living and minimum wage in these countries. Moreover, the same trend is observed when the salary is compared to the average wages of EU-27.

Figure 1. Ratios of living wage and minimum wage with the assumed salary for ACEA operation.

3. As regards the working time in the process, the hours per week are estimated to be 37 for each employee. This value is similar to the average working hours in the counties of EU-27 (Table 5).

4. The developed process could contribute to the job generation in EU-27 by creating 2 working positions.

5. As far as access to material resources is concerned, the level of facility water use is evaluated, compared to the water use of the industrial sector and the total available water of the countries of EU-27.  As Table 6 presents, the percentages for ACEA, SBLA/CUT and OT is 0.01783% for all the case due to the assumption that we consider the same facilities and production capacities for all the cases, regarding the industrial sector it was 0.000596%, regarding the total water available in each country. Luxembourg and Malta indicate very low industrial activity and therefore the percentages of these countries are quite high if compared to the required water for the developed biorefineries. On the other hand, in countries that present high industrial activity (Germany 28 % of the EU total, Italy 16 %, France 12 %, Spain 8 % and Poland 5 % ), the percentages of the industrial sector are equal or below 0.0001%.

6. Finally, the relative contribution of GHG emissions in the average GHG emissions of EU-27 countries is 0.0016% in the case of OT, 0.000015% in the case of SBLA/CUT and 0.00039% in the case of ACEA. Moreover, another remarkable result for GHG emissions is the estimated savings per capita for the three cases.

Economic impact

The calculations carried out considering 5 years of amortization suggest that for a working time of 8 h/d during 264 d/y, so a production of liquid SBO equal to 4170 ton/y (10%wt SBO), the production cost of the SBO is equal to 157 €/ton. Furthermore, the benefit/cost ratio indicates that the production and use of SBO could entail significant savings. The variation in the SBO production cost does not affect these savings considerably. On the other hand, an increase in the SBO concentration in AD or a reduction of post-treatment costs could avoid the above-mentioned benefits. With post-treatment costs lower than 3.54 € and SBO addition higher than 1.77%, the Lifecab process is not feasible anymore.