**4. Conclusions**

In this paper, two methods for GHG emission accounting were compared. First, using the constant GWP values for a 100-year time horizon (GWP100) and second, the time dynamic GWP values for a 100-year time horizon obtained by using the BCCM that takes into consideration the climate system response to the amount, time and decay rate of the emitted pollutant. The GWP100 values are the default emission metric suggested by the IPCC for the annual emission accounting, and it is considered a relatively simple and easy to use the method. Although no scientific evidence backs the use of GWP100 and, more importantly, GWP100 has "no direct estimation of any climate system responses or direct link to policy goals" (Myhre et al. [15]; Cherubini et al. [38]), policymakers widely use the GWP100 values in designing GHG emission mitigation strategies and international agreements, like the Kyoto protocol and Paris agreement.

The results of our study show that the cumulative emissions have di fferent impact profiles when the same amount of total emissions is considered using temporal impacts. The obtained results are also sensitive to the assumed time horizon and can lead to contradicting conclusions. The high sensitivity of the GWP values for the chosen time frame for CH4 and N2O is due to the non-linear nature and di fferent mathematical functions used for approximation of these decay functions. The di fference in the average values of GWP for di fferent time horizons can be substantial, and obtained conclusions can be misleading. When using these averages, a situation is also possible when a longer time horizon diminishes the importance of local and relatively short lifetime emissions, such as CH4. For example, the described situation is evident that in the case of N2O emissions, the time frame of 20 or 100 years does not change the applied GWP values so significantly as they change in the case when CH4 is assessed either in 20 or 100 years.

If the impact on the GTP from CH4 is assessed, it can be seen that CH4 shows a more obvious temperature change e ffect in a shorter run and, in total, contributes to more than half of the temperature change e ffect created by the agriculture in Latvia.

The BCCM facilitates the selection of the time horizon needed for the specific purpose and expresses the results of policy decisions as to the e ffect of emissions on the global temperature change potential. The use of GWP100 is still useful and needed as (at least) two purposes of the emission accounting should be separated—one is for the emission inventory, the other is for the policy planning. The inventory is needed to keep track of the annual emission rates and assess the trends and success achieved in the emissions mitigation in the past, and GWP100 is useful for the purpose.

Meanwhile, policy strategies and instruments aim to achieve some desirable behaviour that may effectively govern a system in the future. And the GWP values obtained by using the BCCM would be much more useful for the purpose. Although "countries and the international community have made significant investments in inventory systems" [16] reconsideration and use of other methodology by the policymakers might eventually be less costly than dealing with consequences of climate change and wrong decisions (sub-optimal policies). Application of the BCCM would facilitate finding more efficient mitigation options for various pollutants, analyze multiple parts of the climate response system at a specific time in the future (amount of particular pollutants, temperature change potential), or analyze different solutions for reaching the emission mitigation targets at regional, national, or global levels.

**Author Contributions:** Conceptualization, L.T., E.D., M.T.K.; methodology, L.T.; Software, E.D.; validation, L.T., E.D.; formal analysis, L.T., E.D., M.T.K.; investigation, L.T.; resources, L.T., E.D.; data curation, L.T.; writing—original draft preparation, L.T.; writing—review and editing, L.T., E.D., M.T.K.; visualization, L.T.; supervision, M.T.K.; project administration, L.T., M.T.K.; funding acquisition, L.T. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was funded by European Union's Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie gran<sup>t</sup> agreemen<sup>t</sup> No 798365.

**Acknowledgments:** This publication is the selected article from the European Biomass Conference and Exhibition (EUBCE) 2019 conference. And the methodology used in the article was initially presented in the EUBCE 2019 conference for the case study on biorefineries under the title Timma L. and Parajuli R. 2019, Time Dynamics in Life Cycle Assessment—Exemplified by a Case Study on Biorefineries. In European Biomass Conference

and Exhibition Proceedings., ETA-Florence Renewable Energies, s. 1599–1603, Lisbon, Portugal, 27/05/2019. https://doi.org/10.5071/27thEUBCE2019-4DO.5.2.

**Conflicts of Interest:** The authors declare no conflict of interest.
