Erratum: Corrigendum to “Exergoeconomic assessment of CHP-integrated biomass upgrading” (Applied Energy (2015) 156 (290–305)(S0306261915008053)(10.1016/j.apenergy.2015.06.047))

The authors regret that there is incorrectness in the market prices derived for wood pellets (WP) and torrefied wood pellets (TWP). Accidentally, both were given as too high. In contradiction to our previous statement the projected average price during the investment period must be 53.4 €/MWh for WP and 48.8 €/MWh for TWP, respectively. In general the conclusion remains the same. The integration of pyrolysis slurry (PS) production remains the most profitable option, whereas the WP case loses its competitiveness to a large extent as a result of the reduced WP market price. Likewise, TWP integration becomes even less competitive. The corrected values influence the results presented in Table 6 and Fig. 6 of the original paper, which are discussed in the following. In Table 1, the now lower projected bio-product market prices decrease the plant's bio-product turnover and thus the profit by 2.31 M€ to 3.54 M€ in the case of WP integration. If the CHP plant is integrated with TWP production the profit is reduced by 1.58 M€ to 1.00 M€. This means that integration of TWP reduces the plant's profit considerably and its application cannot be recommended. WP integration increases the plant's yearly profit by such a small amount (0.38 M€) that an investment of 17.6 M€ could hardly be justified. In contradiction, the integration of pyrolysis slurry (PS) production not only increases the plant's profit by 110% but also justifies an investment if the yearly additional profit of 3.1 M€ is related to the required investment of 23.3 M€. If a transmission fee of 30% of DH turnover is applied TWP integration would result in an annual financial loss of 1.16 M€. It was calculated that the PS integrated system will provide the same profit as the WP system when the average price over the investment period is 65.72 €/MWh, whereas it will remain the same for TWP when the average price is 41.08 €/MWh. This corresponds with the PS price being 31% and 57% lower than projected. In turn, integrated TWP production would be as competitive as PS production if the cost of using coal as a fuel would be as high as 97.22 €/MWh, which is double the price projected in this work. The corrected market prices for TWP and WP also affect the results of the sensitivity study in which the prices for fuel, electricity, district heating, bio-product as well as the investment cost were varied by ±50%. Fig. 1 presents the corrected results. Please note that due to the considerable value changes the range of the abscissae have been adjusted. It is now even more obvious that PS integration clearly reduces the plant's profit dependency on the electricity and the district heat price. That means that, given a constant market price for PS, the PS integrated plant would yield the same profit as the base case CHP plant until a negative power price of approximately −20 €/MWh is reached. Thus PS integration has the potential to increase the plant's competitiveness considerably in times of low electricity prices as currently observed at the Nordic electricity spot market Nordpool. With the corrected market price for WP, the plant reacts now similar than the base case CHP plant on changes of the electricity and DH heat prices. However, dependency on the wood chips price is more distinct, due to the reduced lower profit margin between wood chips and the WP. For TWP integration, the system becomes extremely vulnerable to variations of power and heat prices and financial loss is possible within the variation boundaries chosen. For a DH price being 18% lower than projected the plant would start making losses. Also the influence on the wood chips price is very distinct and even at half the feedstock price the plant would perform equally economical as the WP case. It hence can be concluded that only PS integration has a clear potential to improve the economics of the base case CHP plant at simultaneously reduced dependence on market price variations. The integration of WP increases the profit of the plant by 12%, but the improvement would be zero if the WP price dropped 6% below the projected price. Thus based on our results, the integration of WP and TWP with a CHP plant cannot be recommended. Additional correction: The name of the last author (Reinaldo Giudici) was wrongly spelled in the original article. The authors would like to apologise for any inconvenience caused.

Applied Energy. Volume 181. Pages 590-591