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Describing an overview of the expected role of bioenergy for decarbonization of the energy system, the basic framework and discussion points of the LCA methodology for assessing greenhouse gas （GHG） reduction benefits are summarized. In each of the EU, the U.S. and Japan, a system to ensure the sustainability of liquid biofuels and biomass power generation and heat use has been established by developing standards that include thresholds for GHG reductions calculated by LCA. In these LCA calculations, biomass-derived CO₂ has been assumed to be zero, based on the concept of carbon neutrality. However, the significance of bioenergy use as a climate change countermeasure is being questioned, especially with regard to forest biomass, because of the time required for it to be reabsorbed by natural ecosystems. Bioenergy can be thought as a pioneer in the formation of a framework for confirming sustainability, including the confirmation of GHG reduction benefits, ahead of other decarbonization options. In the light of this experience, it can be recommended to accumulate our knowledge on the use of LCA for policy formulation and implimentation.

The production of chemicals from biomass is the mitigation of fossil-derived chemical production by substituting renewables. Such biomass-derived production can contribute not only to the sustainable production of chemicals but also to the realization of a bioeconomy. However, a consequential analysis of the whole life cycle is essential, and it must work to achieve sustainable agriculture and forestry. This paper reviews the latest research trends, summarizes the perspectives for evaluation at each life cycle stage, and examines the role and challenges of biomass plastics based on life cycle thinking.

This article aimed to summarize the roles and challenges of waste biomass utilization to carbon neutral society. As of 2015, 250 million tons of waste and unused biomass was generated in Japan, of which 70.6% were recycled. Historically, waste biomass, as a renewable energy, is expected to reduce greenhouse gas （GHG） emission and contribute to the development of a sustainable society and revitalization of the regional economy. Carbon neutral society is one of the elements of a new concept of Regional Circular and Ecological Sphere （R-CES）, which was proposed under the 5th fundamental environmental plan in 2018. Utilization of waste biomass plays a major role in the development of R-CES. Under the mid- and long- terms scenario in waste sector for achieving a carbon neutral society proposed in August 2021, material replacement with biomass based materials and energy recovery with high efficiency from waste biomass were introduced as non-energy and energy originated CO₂ reduction measures, respectively. The challenges of estimating GHG emission and reduction on the basis of waste biomass utilization in carbon neutral society are; 1）shifting from energy based substitutions to material based ones with high added values, 2）having a more exact understanding of fossil derived carbon fraction contained in waste biomass, and 3） describing carbon stocks and flow, which may become complicated in the future.

Forests greatly contribute to the global carbon balance by absorbing carbon dioxide from the atmosphere and storing the carbon. Forests play a significant role in mitigating climate change. Wood harvested from forests also functions as carbon stocks until it burns or biodegrades at the end of its life, impacting on the global carbon cycle. This article provides an overview of the roles of forests and wood in the global carbon cycle, their treatment under the Kyoto Protocol and Paris Agreement in the United Nations Framework Convention on Climate Change, and the carbon stock function of forests and wood in Japan. In addition, the article discusses the perspectives for future research on the carbon balance in forests and wood.

To achieve carbon net-zero by 2050, carbon dioxide removal （CDR） technology is needed to offset difficult-to-remove greenhouse gas emissions associated with essential activities. Converting biomass to biochar is one of the low-cost ways to provide CDR at a scale large enough to significantly mitigate climate change. The use of biochar in agriculture has the potential to combine CDR with significant agricultural co-benefits to achieve sustainability. An important milestone in establishing a methodology for estimating biochar addition to soil is the biochar guidance developed by IPCC in 2019. In response, Japan reported biochar in the national greenhouse gas inventory and registered biochar as a new J-credit method for the agriculture sector in 2020. This paper outlined guidance for estimating biochar addition to soil and reviewed the latest trends in the use of biochar in agriculture. Finally, the future prospect for biochar use for sustainable agriculture and carbon neutrality was discussed.

Good Agricultural Practice （GAP） measures environmental conservation and food security achievements in agricultural production. The environmental impacts of agricultural production by farmers who have introduced GAP were compared to those of conventional farmers using a lifecycle assessment based on case study scenarios. The farmers following GAP fertilized with unique method, and their lettuce cultivation global warming potential and eutrophication impacts were lower than those of conventional farmers for both open-field and greenhouse conditions. Unique fertilization techniques did not exhibit a direct relationship with environmental impact; however, an indirect relationship with global warming potential was indicated through the reduction of other inputs including pesticides and lime. The eutrophication impact was greater for conventional farmers, who tend to overfertilize with phosphorous compared to the GAP farmers, who established individual fertilization. Although heating was not employed in the greenhouses in this study, the impacts of greenhouse farming were greater than those of open-field farming. The differences are due to the production process of the greenhouse covering material.

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