Life Cycle Greenhouse Gas Emissions of Wooden Roadside Noise Barriers in Nagano Prefecture

Climate Change Mitigation Potential of Wood Use in Civil Engineering in Japan Based on Life-Cycle Assessment

“…The likely potential for wooden barrier installation in 2050 was then set at half of the current total length of three thousand km (i.e., 1.5 thousand km), while the maximum potential was set as the entire installed length. From this, we obtained annual projected installation lengths of 50 and 100 km/year for the respective cases by dividing the total length of wooden noise barriers in each case by a lifetime of 30 years per barrier [37]. We estimated the potential volume (m 3 /year) of wood use for wooden noise barriers in 2050 by multiplying the annual installed length (km/year) by the usage volume of wood product per unit length (0.15 m 3 /m) [37].…”

“…From this, we obtained annual projected installation lengths of 50 and 100 km/year for the respective cases by dividing the total length of wooden noise barriers in each case by a lifetime of 30 years per barrier [37]. We estimated the potential volume (m 3 /year) of wood use for wooden noise barriers in 2050 by multiplying the annual installed length (km/year) by the usage volume of wood product per unit length (0.15 m 3 /m) [37]. As in the other cases, values from 2018 to 2049 were interpolated using a sigmoid curve (Figure 1).…”

“…where ACSW (t-CO 2 eq/year) is the year-to-year change in the amount of carbon stored in wood, CSW (t-CO 2 eq) is the carbon storage in wood in a given year, WS (m 3 ) is the volume of wood stock used in civil engineering, DW (t/m 3 ) is the density (oven dry mass over air dry volume) of wood (0.45 for coniferous wood) [43], CC (t-C/t) is carbon content of oven-dried wood (0.50) [43], CD (t-CO 2 /t-C) is conversion factor from the weight of carbon to the weight of carbon dioxide (=44/12), WU (m 3 /year) is the wood product use potential in civil engineering as described in Section 2.1, LT (-) is the lifetime function, n (years) is the number of years elapsed, r (-) is the rate of decrease (0.2), and a (years) is the civil engineering lifetime (half-life) (infinite for log piles and wooden check dams; 10 years for woodchip-paved walkways and wooden guardrails; 30 years for wooden noise barriers) [33][34][35][36][37]. Additionally, t represents the year, and i is an index denoting the respective wood applications (log pile, wooden check dam, woodchip-paved walkway, wooden guardrail, and wooden noise barrier).…”

“…There are few prior research cases of LCA targeting wood use in civil engineering in Japan. Although studies have analyzed the life-cycle GHG emissions from wood use in civil engineering and the emission reductions resulting from substituting wood for non-wooden materials [33][34][35][36][37], these studies have targeted only individual applications, including log piles [33], wooden check dams [34], woodchip-paved walkways [35], wooden guardrails [36], and wooden noise barriers [37]. The future availability of wood for civil engineering structures in the country as a whole and the associated nationwide potential for climate change mitigation remain unclear.…”

“…Many prior studies [3,7,16,27,[34][35][36][37] assumed the biogenic carbon (CO 2 ) balance of wood in the LCA and the CFs to be carbon-neutral. In other words, they had no effect on the CO 2 concentrations in the atmosphere; thus, the biogenic carbon balance was considered zero.…”