Comparison of LCCO2 on detached houses between Hokkaido and Finland

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Comparison of LCCO2 on detached houses between Hokkaido and Finland

Oi Marina, Mori Taro

HU, Sapporo, Japan

Abstract. In Japan, houses whose net energy consumption per year is generally below zero have been built. However, the impact of these houses on the environment throughout the life cycle of building is not evaluated. Therefore, this study evaluated the life cycle carbon dioxide (LCCO2) of detached houses in Hokkaido, Japan, from material production to disposal and compared LCCO2 of detached houses in Hokkaido and Finland. In this result, LCCO2 of detached houses in Hokkaido was larger than those of Finland. And in Hokkaido, the amount of CO2 emission at materials production stage and operation stage was the largest in life cycle of building. Therefore, we concluded that we should reduce CO2 emission at materials production stage and operation stage in order to reduce LCCO2 of detached houses in Hokkaido. In addition, as the ways to reduce it, we found that we should use renewable energy and plant-based materials throughout the life cycle of building.

Keyword LCCO2, carbon neutral, CO2 emission, renewable energy, detached house, global warming

Ои Марина, Мори Таро Университет Хоккайдо, Саппоро, Япония.

СРАВНЕНИЕ УРОВНЯ ДВУОКИСИ УГЛЕРОДА (СОг), ВЫДЕЛЯЕМОЙ ОСОБНЯКАМИ НА ХОККАЙДО И В ФИНЛЯНДИИ

energy conservation architecture emission

Абстракт. В Японии построены дома, где чистое потребление энергии в год ниже нуля, однако их влияние на окружающую среду в течение всего срока эксплуатации не было оценено. В этом исследовании была проведена оценка жизненного цикла двуокиси углерода (LCCO2) для отдельностоящих особняков на Хоккайдо, Япония, от производства материалов до утилизации, после чего результат сравнивался с тем же показателем домов в Финляндии. В результате показатели уровня выделения двуокиси углерода (LCCO2) домами на Хоккайдо оказались выше, чем в Финляндии. На Хоккайдо количество выбросов СО2 оказалось самым большим на стадии производства материалов и эксплуатации. Поэтому мы пришли к выводу, что следует сократить число выбросов СО2 на этапе производства материалов и на этапе эксплуатации, чтобы уменьшить LCCO2 домов на Хоккайдо. Кроме того, в качестве способов снижения мы обнаружили, что следует использовать возобновляемые источники энергии и природные материалы на всем протяжении жизненного цикла здания.

Ключевые слова: LCCO2, углеродно-нейтральный, выделение СОг, возобновляемая энергия, особняк, глобальное потепление.

Introduction

In recent years, energy conservation has been promoted in the field of architecture to prevent global warming, and many attempts have been made to achieve ZEH by actively using passive technologies and renewable energy. On the other hand, in cold regions where the use of renewable energy is difficult, there are attempts to achieve carbon neutrality, mainly in Europe, rather than zero energy. However, there are few examples of evaluating the emissions and impacts lof greenhouse gases such as CO2 throughout the life cycle of buildings. Therefore, this study evaluated LCCO2 of detached houses in Hokkaido, Japan, from material production to disposal. In addition, the ways to achieve carbon neutral buildings in Hokkaido were investigated by comparing LCCO2 with Finland, which has been promoting zero emissions.

Evaluation Method of LCCO2

In this study, life cycle of building was divided into 4 stages of material production, repair, operation, and disposal for 60 years as the evaluation period. The amount of CO2 emissions were calculated using the amount of materials and energy generated in each stage, and the sum of these was evaluated as LCCO2.

As shown in Figure. 1, the case in Hokkaido was calculated by inputting data of materials MiLCA, which is an LCA calculation tool created based on ISO standards. MiLCA can calculate the amount of CO2 emissions by inputting the mass, volume, and price of an object. In this study, we first calculated the type and quantity of materials from the estimate sheet and converted them into mass. After that, we entered the quantity of materials into MiLCA and calculated the amount of CO2 emissions at the material manufacturing stage. The amount of CO2 emissions at the repairing stage was calculated for exterior wall painting, windows and roofs. The amount of CO2 emissions at the waste stage was divided into two categories: disposal as industrial waste and recycling of wood. However, the energy used to transport raw materials to manufacturing plants and to use machinery in construction and demolition work, and the energy used to treat waste generated at stages other than disposal are excluded from the calculation because accurate data were not available and the overall impact was small. Materials that do not contain specific figures and have little impact on the total are excluded in the calculation of the material manufacturing stage.

In the case in Finland, a virtual carbon-neutral detached house was used, with data calculated by collaborators using a database based on EN standards.

Figure. 1 MiLCA

The detached houses for comparison

Table 1 shows basic information on detached houses in Hokkaido and Finland, where four people are expected to live. The case in Hokkaido is two houses of the wooden frame construction method which satisfied the energy saving standard of Japan. The case in Finland, on the other hand, uses common local materials but covers buildings that are actively using renewable energy or CLT.

Table 2 shows the parameters of energy consumption during the operation and disposal stage. The energy source for Hokkaido-A, В (1), (2) and (3) was propane gas, and the disposal method was changed as shown in Table 2. The energy sources of Hok- kaido-A and В (4) were wood chips and PV, and wood was reused at the disposal stage. On the other hand, the energy sources of Finland-A, В (1) (2) are PV and wind power generation, and the disposal method was changed as shown in Table 2.

Table 1. Basic information on detached houses in Hokkaido and Finland

Table 2. The parameter of energy consumption and disposal method

Result

Figure. 2 shows the LCCO2 evaluation results based on the parameters in Table.2. In Figure.2, the LCCO2 of Hokkaido-A, В (1), (2) and (3) is much larger than that of Fin- land-A, В (1) and (2), and the amount of CO2 emissions during operation is the largest. Even if the means of disposal is changed to reuse of chips and wood, the amount of LCCO2 has hardly decreased. Comparing Hokkaido-A, В (1) (2) (3) and Finland-A, В (1) (2) in Figure.3, the amount of CO2 emissions at the material manufacturing and operational stages in Hokkaido are higher than Finland. In other words, in order to reduce LCCO2, it is necessary to reduce CO2 emissions at the material manufacturing and operation stages.

Figure 2. Evaluation results of LCCCh

Figure 3. The amount of CO2 emission for each stage of life cycle of building

Examination of LCCO2 reduction method

Figure.4 shows the quantity of main materials. The case in Hokkaido uses almost half the amount of wood as Finland does, but has about 65 times more concrete and 10 times more gypsum board, resulting in higher CO2 emissions from the manufacturing process. In other words, plant-based materials such as wood should be used in the material manufacturing process to reduce CO2 emissions during the material manufacturing process.

Next, comparing (2) and (3) of Hokkaido-А, В (1) and (4) in Figure.2, the CO2 emissions in (4) using renewable energy by converting energy sources into PV and wood chips were 75 ~ 85% lower than those in (1), (2) and (3) using propane gas. In other words, in order to reduce CO2 emissions during operation, renewable energy should be used during the operation stage.

Comparing Finland-A, В (1) and Finland-A, В (2) in Figure.2, LCCO2 of (2) is less than (1). This is because, as shown in Figure.З, CO2 is generated during chip manufacturing, which increases CO2 emissions at the disposal stage. However, when comparing Hokkaido-A, В (4) and Finland-A, В (2) in Figure.2, both use renewable energy and use the same disposal method, but LCCO2 in Hokkaido is higher. As shown in Figure.3 for Hokkaido-A,В (4) and Finland-A,В (2), the ratio of CO2 emissions at the disposal stage is small, and there is a large difference between CO2 emissions at the material manufacturing stage and those at the operational stage. In other words, recycling in Hokkaido is less effective in reducing LCCO2.

Therefore, in order to reduce LCCO2 emissions in Hokkaido, renewable energy and plant-based materials should be actively used at the material production stage and during operation.

Figure 4. The quantity of main materials

Conclusion

We needed to reduce LCCO2 of detached houses in Hokkaido in order to have a positive effect on global wanning. However, LCCO2 of detached houses in Hokkaido was much larger than Finland, which has been promoting zero emissions and carbon neutral. In addition, detached houses in Hokkaido had a high proportion of CO2 emission at both the material production stage and operation stage. Therefore, in order to reduce LCCO2 of detached houses in Hokkaido, we should particularly reduce CO2 emission at material production and operation stage. Then considering the results of comparison of LCCO2 between Hokkaido and Finland, as the ways to reduce LCCO2 of detached houses in Hokkaido, we found that we should use plant-based materials such as wood at material production stage and renewable energy at operation stage. This study revealed that energy conservation in the field of architecture had few effects to reduce greenhouse gas such as CO2.

Reference

1. Japan Environmental Management Association for Industry: LCA System MiLCA ver.2.0, MiLCAv2 Guidebook.

2. VTT: Ecolnvet 3.2 database, 2019.

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