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This study provides information on the disaster waste management practices and disposal methods employed in Kathmandu Valley for debris generated by the Gorkha Earthquake on April 25, 2015. We also quantify the amount of building debris generated and managed at destinations within the core city area of Kathmandu Valley, which was diverted from the government-proposed disposal site. This research involved field visits, interaction with communities, meetings with officers related to debris management, and reference to published reports. Disaster waste management in Nepal included the reuse/recycling of building materials in new construction or as filling materials in land development. Debris were also disposed on low-lying areas, down the cliff, and river bank; however, the disposal method was open dumping. Of the estimated 3.23 million tons of potential debris generated in the core city area of Kathmandu Valley, 1.07 million tons were managed 2 years after the Gorkha Earthquake, of which 0.63 million tons were disposed on river banks, along the ring road, and in open spaces, and the remaining 0.44 million tons were salvaged for reuse or sold for recycling or disposed in other isolated areas. Approximately 2.17 million tons of building debris is yet to be managed.

Numerous reports have elucidated different statistical approaches to identify temporal trends in atmospheric persistent organic pollutant (POP) time series. However, the correlation of industrial activity with concentrations of atmospheric POPs in Japan has not yet been determined. Herein, a panel data analysis of a 16-year monitoring program (2003–2018) conducted by the Japanese Ministry of Environment was used to investigate a range of POPs in the atmosphere above Japan. This work focuses on polychlorinated biphenyls (PCBs), polychlorinated naphthalenes (PCNs), polybrominated diphenyl ethers (PBDEs), hexachlorobenzene (HCB), and pentachlorobenzene (PeCBz) collected each year at 53 sites across Japan. The panel analysis revealed that PCB, PCN, and PBDE concentrations were influenced by a combination of factors including year, industrial activity (municipal and industrial waste incinerators, cement kilns, steel industry, and secondary zinc production), population, temperature, and atmospheric boundary layer. However, HCB and PeCBz were not significantly affected by these factors. Industrial activity showed stronger positive correlations with all homologues of PCBs, PCNs, and PBDEs as compared to those demonstrated by population. Significant decreasing trends were identified for the atmospheric ∑ P B D E s (half-life t1/2 = 9.4 years), ∑ P C N s (t1/2 = 8.9 years), and ∑ P C B s (t1/2 = 13.5 years) concentrations, while HCB and PeCBz showed slightly increasing or steady levels. As a statistical tool, panel data analysis can contribute to the assessment of spatial and temporal trends of POPs at a national scale, while elucidating different behavioral responses to numerous environmental variables.

Significant quantities of building waste were generated from collapsed residential and dilapidated buildings as a result of the disastrous Gorkha earthquake in Nepal on April 25, 2015. In this study, in relation to the field damage investigation of the earthquake hit area and based on the building types, different types of building waste produced from each building are estimated and evaluated. An estimation procedure was established to assess the amount of debris resulting from earthquake. In Kathmandu Valley, different types of buildings generated different quantities of building waste per unit area, and the values for these building types ranged from 1.90 to 3.23 ton m− 2 in weight and 0.89 to 1.57 m3 m− 2 in volume respectively. Residential buildings in Nepal generated a larger amount of waste per unit area (ton m− 2) than buildings in Japan and China. Waste amounts (excluding that in the foundation) generated by public reinforced concrete buildings in Nepal were similar to the amounts generated by reinforced concrete buildings in Japan and China. Wooden buildings had the highest volume per unit area of building waste in Japan, as compared to those in Nepal and Sri Lanka. These results can be used to estimate the amount of building debris that must be cleared for emergency response after a disaster. This information is vital to pre-disaster planning to establish disaster management protocols for smooth recovery operations.

We estimated the in-use stocks of polybrominated diphenyl ethers (PBDEs) in Japan using a population balance model. The estimation is based on the domestic demand of PBDEs and the assumed survival rate of these products. Two cases relevant to the future regulation of commercial deca-BDE are considered, namely (1) deca-BDE declines at the same rate as the current rate of decline, and (2) deca-BDE is discontinued after 2020. The estimates of the decreasing rates of in-use penta-, octa-, and deca-BDE stocks were proportional with the measured decreases in the atmospheric concentrations of these substances. The in-use penta- and octa-BDE stocks could be depleted in the near future (500 and 60 tonne in 2013, and an estimated 20 and

The purpose of this study was to quantify the life-cycle greenhouse gas (GHG) emissions reduction that could be achieved by replacement of fossil-derived materials with biodegradable, biomass-based materials for household plastic containers and packaging, considering a variety of their treatment options. The biomass-based materials were 100% polylactide or a combination of polybutylene succinate adipate and polylactide. A scenario analysis was conducted considering alternative recycling methods. Five scenarios were considered: two for existing fossil-derived materials (the current approach in Japan) and the three for biomass-based materials. Production and waste disposal of 1 m3 of plastic containers and packaging from households was defined as the functional unit. The results showed that replacement of fossil-derived materials with biomass-based materials could reduce life-cycle GHG emissions by 14–20%. Source separation and recycling should be promoted. When the separate collection ratio reached 100%, replacement with biomass-based materials could potentially reduce GHG emissions by 31.9%. Food containers are a priority for replacement, because they alone could reduce GHG emissions by 10%. A recycling system for biomass-based plastics must be carefully designed, considering aspects such as the transition period from fossil-derived plastics to biomass-based plastics.

Open dumping sites in Surabaya and Palembang, Indonesia, have been studied to investigate emissions of polychlorinated dibenzo-para-dioxins and dibenzofurans (PCDD/Fs) and dioxin-like polychlorinated biphenyls (DL-PCBs), as well as the resulting soil contamination that might be caused by open burning of municipal solid waste. The emission factors of the waste residue, accounting for the ratio of waste burned, have also been characterized. The concentrations of PCDD/Fs and DL-PCBs in soil from Palembang were 61–310 pg-TEQ/g (dry weight) and 6.3–32 pg-TEQ/g, respectively. In Surabaya, very low levels of PCDD/Fs and DL-PCBs, ranging from 0.075 to 0.098 and 0.00032 to 0.095 pg-TEQ/g, respectively, were observed in soil for an open dumping site that included a top cover layer of soil above the compacted waste. The large difference in concentrations can be explained by the fact that open burning of waste is the source of PCDD/Fs and DL-PCBs. The emission factors for the residue for PCDD/Fs ranged from 27 to 140 pg-TEQ/g, and a sensitivity analysis found that the maximum emission factor to the residue could be 5600 pg-TEQ/g. Our results indicate that emissions of PCDD/Fs can be controlled by modifying the open dumping process to one that involves depositing soil layers on top of the compacted waste.

In this study, we aim to determine the correlation between the height of the atmospheric boundary layer (ABL) and the concentrations of polybrominated diphenyl ether (PBDE) congeners, in an effort to improve comprehension of the atmospheric behavior of PBDEs. We used the PBDE data in air (n = 298), which were measured by the Japan Ministry of Environment (JMOE) at 50 sites across Japan during the period 2009-2012. The height of the ABL, which directly affects the PBDE concentrations in the near-surface air, was estimated by employing data retrieved from the Japanese global reanalysis (JRA-55) database, using the parcel and Richardson number method. The ABL has shown a strong inverse relationship with BDE-47 and BDE-99 (p0.01). In contrast, there was less correlation between BDE-209 and the ABL (p = 0.258). These differing behaviors could be explained by differences in particle size distribution of PBDEs, where BDE-47 and BDE-99 are associated with gas phases and fine particles and BDE-209 is associated with coarse particles. To our knowledge, this paper represents the first large-scale analysis of correlations between the ABL and the concentrations of PBDEs in the air.

A simplified life cycle assessment was conducted to estimate greenhouse gas (GHG) emissions and energy production from each component of biogenic waste treated in an open dumping site, and by composting, anaerobic digestion, and incineration employed with additional options. The impact of uncertainties and sensitivities of the parameters in the treatment methods were investigated. We conducted a sensitivity analysis to identify the most sensitive parameters, and we discussed the relationship between uncertainty and sensitivity. Our results revealed that the moisture content of food waste and the biomass-derived carbon and methane concentration of the landfill gas of biogenic waste subjected to open dumping are the most sensitive parameters across all the treatment methods. The net GHG emissions from food waste treated in an open dumping site ranged over ten times (0.30 − 3.67 Gg CO2 eq/Gg). In addition, by employing additional options for the open dumping site, including soil cover, a landfill gas collection system, shifting to a semi-aerobic condition, and energy conservation by using a gas engine, we found that the net GHG emissions could be reduced by 10, 27.9, 37.4 %, and up to 56.7 %, respectively. Shifting to a semi-aerobic system is the most effective method for reducing GHG emissions, followed by landfill gas collection.

本稿では, 自治体固有の影響や年度固有の影響を考慮したパネルデータ分析 (2001-2007) により, 産業廃棄物税 (以下, 産廃税) による全産業廃棄物および品目別 (廃プラスチック類, 汚泥, がれき類) の課税効果を推定した. 特に, 産廃税制度設計要因として徴税方法別の課税効果や焼却施設への課税効果について検証した. この結果, 特別徴収方式の産廃税導入により, 全産業廃棄物, 汚泥, がれき類に対する最終処分量の削減効果, ならびに全産業廃棄物, 廃プラスチック類, 汚泥に対する中間処理量の増加作用が推定された. また, 埋立処分と焼却に対して課税した場合, 埋立処分のみに課税した場合に比べて, 廃プラスチック類で4割, 汚泥で3割の中間処理量の削減効果があるが, がれき類ではその効果は表れないことが確認された. 品目別で課税効果に差が見られ, 廃棄物処理フローへの影響がそれぞれ異なることが確認された., In Japan, 27 prefectures have implemented an industrial waste tax system comprised of two taxation methods: payment by self-assessment, and payment by special collection. In this study, we estimate waste reduction and recycling effects resulting from the implementation of the industrial waste tax using panel data from 47 prefectures during the period 2001 to 2007. The study looked at the total amount of industrial waste being generated and the three categories of industrial waste (plastic waste, sludge, and debris). The paper also analyzes the impacts on waste flow caused by these two taxation methods and taxation on incineration facilities. First, results verified that the industrial waste tax using payment by special collection had a greater effect on waste reduction with regard to final disposal amounts for total industrial waste, sludge, and debris. Moreover, taxation increased the amount of intermediate treatment for total industrial waste, plastic waste, and sludge. Next, we calculated that taxation on incineration facilities would reduce the intermediate treatment amount of plastic waste by 40 percent and that of sludge by 30 percent. Finally, we confirmed that the effects of the industrial waste tax will vary across the different waste categories.

国内都市部の一例として京都市を対象に，都市ごみ中のバイオマスである厨芥類および紙類の賦存量を推定した。厨芥類の発生量は22.2万ton-wet/年，紙類は22.3万ton-wet/年であり，ほぼ全量が焼却処理されている。これらを対象に利用システムの温室効果ガス (GHG) 削減効果およびエネルギー回収率を評価した結果，「バイオガス化 (高温乾式メタン発酵)＋ガスエンジン発電 (GE)」は既存の「直接燃焼＋蒸気発電」，「直接燃焼＋堆肥化」よりも有利であった。また，バイオガス発電時の廃熱を利用する超高温可溶化技術を組み込んだ可溶化システムでは，現状の乾式方式に対してエネルギー回収率およびGHG削減効果で27%の向上が見込まれた。さらに，バイオガスの燃料電池利用により，GE利用の最大1.7倍まで効果向上が期待された。国内温室効果ガスの削減に向けて都市ごみ中バイオマスの高度なエネルギー変換技術の普及が望まれる。

Occurrence of flame retardants (FRs) in the indoor environment of highly flame-retarded public facilities is an important concern from the viewpoint of exposure because it is likely that FRs are used to a greater degree in these facilities than in homes. For this study, brominated flame-retardants (BFRs) and organophosphate flame-retardants and plasticizers (OPs), and brominated dibenzo-p-dioxins/furans (PBDD/DFs) were measured in eight floor dust samples taken from a Japanese commercial hotel that was assumed to have many flame-retardant materials. Concentrations of polybrominated diphenylethers (PBDEs) and hexabromocyclododecanes (HBCDs) varied by about two orders of magnitude, from 9.8–1700 ng/g (median of 1200 ng/g) and from 72–1300 ng/g (median of 740 ng/g), respectively. Concentrations of the two types of BFRs described above were most dominant among the investigated BFRs in the dust samples. It is inferred that BFR and PBDD/DF concentrations are on the same level as those in house and office dust samples reported based on past studies. Regarding concentrations of 11 OPs, 7 OPs were detected on the order of micrograms per gram, which are equivalent to or exceed the BFR concentrations such as PBDEs and HBCDs. Concentrations of the investigated compounds were not uniform among dust samples collected throughout the hotel: concentrations differed among floors, suggesting that localization of source products is associated with FR concentrations in dust. Passive air sampling was also conducted to monitor BFRs in the indoor air of hotel rooms: the performance of an air cleaner placed in the room was evaluated in terms of reducing airborne BFR concentrations. Monitoring results suggest that operation of an appropriate air cleaner can reduce both gaseous and particulate BFRs in indoor air. Keywords: Flame retardants, Hotel, Dust, Air

Aimed to give a preliminary image of dioxin pollution in China, chemometric analysis was performed to determine background dioxin levels during the period 1994-2002 and potential emission sources. Using principal components analysis (PCA), the congener profiles of 71 sediment samples from rivers, lakes, and sea bays around China were compared with the congener profiles of various known or suspected industrial, residential, and municipal dioxin sources to determine whether the dioxin residues typically found in a broad range of potential environmental sources could explain the presence of these chemicals in China. It was found that the background dioxin levels of China were similar to those of lightly polluted samples from other countries during the period 1994-2002. Primary ferrous ore sintering and secondary lead and aluminum smelters were the major sources of dioxin emission in China. Chloranil and wastewater from chemical plants, sodium pentachlorophenate, and pulp bleaching were also important sources of dioxin emission. Open burning of e-waste as well as diesel-fueled and leaded gas-fueled vehicles were additional possible sources of dioxin. In contrast to other countries, in China, flue gases from incineration of municipal waste, hazardous waste, and medical waste might be minor sources of dioxin emission.

We used polybrominated diphenyl ether (PBDE) data in air at 38 sites across Japan (2009-2012), which were measured by the Japan Ministry of Environment (JMOE), to elucidate the time trend and seasonality of atmospheric PBDEs. In order to address few (7% for BDE-47) to many (63% for BDE-153 and 183) non-detect data, Tobit model, also called a censored regression model was used. The model revealed that the concentrations of PBDE congeners were influenced by a combination of year, temperature, rainfall rate, and population density. Greater declines were observed for BDE-47, -99, -153 and -183 (-21, -25, -17, -23%/year, p < 0.05) than for BDE-209 (-6%/year, p = 0.065). These trends were consistent with the estimated trends of penta-, octa- and deca-BDE contained in in-use products based on domestic demand for PBDEs in Japan and product lifespan. Seasonal patterns were opposite for light congeners (BDE-47 and -99), which increased with temperature, and heavy congeners (BDE-183, and -209), which decreased with temperature. Temperature-dependent emission (evaporation) for light congeners and temperature-independent emission (abrasion) for heavy congeners, coupled with seasonality of atmospheric boundary layer height, might explain these seasonal patterns. Human population density showed a positive correlation with all PBDE congener concentrations, whereas PBDEs showed negative correlation with rainfall rate.

Atmospheric emissions of deca-brominated diphenyl ether (DBDE) in Japan were estimated based on the material flow of DBDE products and their emission factors. In 2002, the demand for DBDE in Japan was 2200 ton/year and the stock level was about 60 000 ton. The DBDE flow into the waste stream was estimated to be about 6000 ton/year and the flow out through second-hand product exports was more than 700 ton/year. Home appliance recycling facilities dismantle and crush domestic wastes containing about 600 ton of DBDE annually. Material recycling of crushed plastics is not commonly practiced as yet. Emission factors from plastics processing (2 × 10−9–1 × 10−7), textile processing (9 × 10−7), home appliance recycling (8 × 10−9–5 × 10−6), and waste incineration (1 × 10−7–2 × 10−6) were estimated using field measurement data. The DBDE emission rate through house dust during the service life of final products (2 × 10−7–9 × 10−7 per year) was estimated using the DBDE concentration in dust and the amount of dust in used televisions. Emission factors from previous studies were also used. The estimated total DBDE emission was 170–1800 kg/year. These results suggest the necessity of characterizing emissions during the service life of products, which is essential information for formulating an appropriate e-waste recycling strategy.

自動車用鉛バッテリーのリサイクル・廃棄フローモデルを作成し, インターネットアンケート調査から退蔵バッテリー残存率関数を定め, 静脈フローを推定した。補修用バッテリー販売時の廃バッテリー回収率は, ガソリンスタンド・整備業では10割に近く, カーショップで約8割, ホームセンターで約5割, 平均回収率は85%で, 約230万個/年が未回収と推定された。不要となった後も家庭内で保管 (退蔵) されるバッテリーのストック数は約500万個, 平均滞留年数は約2.2年と推定された。これらの結果と統計等を元に推定した2003年度の不要バッテリーのリサイクル率は, 精錬業で原料利用した国内再生率84%, 国内解体率87% (解体後に得られる巣鉛の輸出を含む) , 中古バッテリー輸出を含む国内回収率89%であった。残る11%は, 中古車上の車載輸出 (約5%) , 焼却・埋立, 不法投棄, 退蔵純増に至ると推定された。

バイオ資源・廃棄物等について, 各市町村の統計データを基に賦存量を推定し, 資源品目毎に1自治体あたりおよび1人あたり賦存量と人口規模との関係を整理した。農産系・林産系・畜産系バイオマスでは人口規模が小さいほど1人あたり量や累積賦存量 (一定の人口規模の自治体での総量) が多くなるのに対して, 廃棄物系バイオマスでは逆の傾向を示すことが明らかになった。また, 厨芥類を対象として, 燃料電池でのバイオガス利用を含む4つの処理シナリオを設定し, 人口規模小の地域 (農村部) および人口規模大の地域 (都市部) をモデルに温室効果ガスを評価項目としたケーススタディを行った。焼却や堆肥化と比較してメタン発酵によるバイオガス回収・発電利用はCO2排出量が少ないこと, 燃料電池はガスエンジンよりもCO2削減効果が大きいこと, 農村部と都市部の違いがシナリオの評価に影響することが示された。

低濃度PCB汚染油の処理対象基準濃度設定に資するため, 廃油処理に伴う作業者および周辺居住者のリスクを評価した。廃油中PCB濃度が50mg/kgのとき居住者の追加的曝露量推定値はPCB・ダイオキシン類のTDIの1/20以下であり, 作業環境のダイオキシン類濃度推定値は, 管理濃度2.5P9-TEQ/m3の1/100以下であった。また, 5mg/kg以下で作業者の体内負荷量最大値は個人差を考慮しない場合のNOAEL以下となった。処理対象外となる廃油の平均PCB濃度は, 処理基準が20mg/kgのとき4.8mg/kgと推定された。PCBの環境放出量は日本の現在の年間排出量の1%以下と推測された。

Intake fractions (iFs) for emissions to air, water, and soil for 17 PCDDs/DFs and 12 Co-PCBs were calculated with a level III multimedia model and a food-chain exposure model in succession. The two integrated models were tested by comparing the predicted and measured concentrations in the environment and by comparing intakes through food. Measurement-based iFs were also calculated and compared with the model-based iFs. The air concentrations predicted by the fate model were close to the median of the observed concentrations, whereas the predicted soil and water concentrations were one-third to one-tenth the observed concentrations. This difference was large in case of PCDDs and Co-PCBs, which was explained by the past pollution such as commercial PCB products and PCDD impurities in chloronitrofen (CNP) and pentachlorophenol (PCP). For fish, the predicted and observed exposures agreed well each other. For meat and milk, the predicted exposures were about 10 times the observed exposures for PCDDs/DFs, whereas the predicted and observed values agreed well for Co-PCBs. When the model was modified to consider feeding of fish meal to livestock and geographic bias in feed-grass production, the predicted congener profile was comparable to the measured profile. The comparison also suggested that chickens should be modeled separately from other terrestrial livestock. The model-based iFs for air emission of OCDD and 2378-TCDD were 0.001% and 0.1%, respectively. The iFs of most Co-PCBs were higher than those of PCDDs/DFs. These iF differences suggest the importance of the fate factor in assessing emissions of the 29 congeners.

PCB廃棄物処理事業の費用効率性を既往対策 (廃棄物焼却炉ダイオキシン類対策事業) と比較した。比較には, 同一の環境運命・曝露モデルによって算出した摂取量削減量あたりのコストを用いた。対策コストは既報の値を用い, 摂取量削減量は既報の放出量削減量をモデルの入力として, 環境運命・曝露モデルによって推定した。評価期間は, 現世代にとっての費用効率性という視点から, 30年間とした。PCB処理事業による摂取量削減量の上限は, 大気放出削減時0.8g-TEQ, 水系放出削減時5.79-TEQ, 土壌放出削減時1.6g-TEQと推定され, 焼却炉対策事業での摂取量削減量は3.5～11g-TEQと推定された。また, 摂取量削減量あたりコストはPCB処理事業で0.27～1.9億円/mg-TEQ, 焼却炉対策で0.67～2.1億円/mg-TEQと同程度となった。PCB処理事業は焼却炉対策と同程度の費用効率性を有するといえる。

PCB廃棄物の保管継続と処理促進とのリスクを比較した。モニタリングデータとモデル推定値との比較より, 保管継続に伴うPCB放出量の上限は, 土壌排出でPCB不明・紛失量と同程度, 大気および水系排出でその1/10程度と推定された。Co-PCB個人曝露量は, 保管継続時の上限が数pg-TEQ/人/日であり, 処理促進時は処理施設周辺で0.1～0.7pg-TEQ/人/日, その他国内でさらに2～4オーダー低く推定された。人口を乗じた曝露総量では施設周辺以外の比率が高く, 国外も数割を占めた。地域別の個人曝露量および曝露総量の推定結果は, 局地的な効果と大局的な効果の双方を考慮することの必要性を示唆した。

家庭由来食品残渣の処理方式4種 (焼却, メタン発酵+残渣焼却, メタン発酵+残渣堆肥化, 堆肥化) を対象としてLCAを行った。環境影響領域として地球温暖化, 酸性化, 埋立地消費, 有害物質によるヒトへの健康影響をとりあげDistance to Target (DtT) 法による重み付け評価をした。有害物質としてはダイオキシン類および重金属類を取り上げ, 3種のMackayモデルを用いた特性化を試みた。メタン発酵を含むシナリオは含まないシナリオに比べ, 環境負荷を低減する傾向にあった。堆肥化は焼却処理に比べ温室効果ガス排出が多いが, DtT法による評価では埋立量削減の効果がこれを上回った。有害物質による影響は用いる特性化係数によって異なり, 定常モデルでは農地への重金属排出による影響がダイオキシン類の大気排出による影響より大きいと評価されたが, 100年間の影響を見る動的モデルでは, ダイオキシン類の大気排出が支配的な影響を持つと評価された。

ヘキサクロロベンゼン (HCB) 排出量の推定と動的環境挙動モデルによるHCBの運命予測を組み合わせ, 底質中HCB濃度トレンドを推定した。HCB発生源として農薬 (PCP, PCNB, TCTP) 不純物, テトラクロロエチレン蒸留残渣焼却, 都市ごみ焼却を考慮した。この底質トレンド推定結果を琵琶湖北湖東岸と大阪湾西宮沖の底質コア濃度実測値と比較した。底質到達への時間遅れにより, HCB排出量トレンドとHCB底質濃度トレンドの差違を部分的に説明できた。琵琶湖と大阪湾の底質トレンドの違いは, 発生源と流入経路の違いを反映したものと思われる。

[Purpose]Source-separated collection of food waste has been reported to reduce the amount of household waste in several cities including Kyoto, Japan. Food waste can be reduced by various activities including preventing edible food loss, draining moisture, and home composting. These activities have different potentials for greenhouse gas (GHG) reduction. Therefore, we conducted a life-cycle inventory analysis of household waste management scenarios for Kyoto with a special emphasis on food waste reduction activities. [Methods]The primary functional unit of our study was “annual management of household combustible waste in Kyoto, Japan.” Although some life-cycle assessment scenarios included food waste reduction measures, all of the scenarios had an identical secondary functional unit, “annual food ingestion (mass and composition) by the residents of Kyoto, Japan.” We analyzed a typical incineration scenario (Inc) and two anaerobic digestion (dry thermophilic facilities) scenarios involving either source-separated collection (SepBio) or nonseparated collection followed by mechanical sorting (MecBio). We assumed that the biogas from anaerobic digestion was used for power generation. In addition, to evaluate the effects of waste reduction combined with separate collection, three food waste reduction cases were considered in the SepBio scenario: (1) preventing loss of edible food (PrevLoss); (2) draining moisture contents (ReducDrain); and (3) home composting (ReducHcom). In these three cases, we assumed that the household waste was reduced by 5%. [Results and discussion]The GHG emissions from the Inc, MecBio, and SepBio scenarios were 123.3, 119.5, and 118.6 Gg CO2-eq/year, respectively. Compared with the SepBio scenario without food waste reduction, the PrevLoss and ReducDrain cases reduced the GHG emissions by 17.1 and 0.5 Gg CO2-eq/year. In contrast, the ReducHcom case increased the GHG emissions by 2.1 Gg CO2-eq/year. This is because the biogas power production decreased due to the reduction in food waste, while the electricity consumption increased in response to home composting. Sensitivity analyses revealed that a reduction of only 1% of the household waste by food loss prevention has the same GHG reduction effect as a 31-point increase (from 50% to 81%) in the food waste separation rate. [Conclusions]We found that prevention of food losses enhanced by separate collection led to a significant reduction in GHG emissions. These findings will be useful in future studies designed to develop strategies for further reductions in GHG emissions.