*9.1.4 Ozone (O3) and waste management*

Some controls bear more benefits: mitigate climate change, and upgrade agriculture and health. Ozone control with methane reduction embodies such impacts [52, 168]. Tropospheric ozone is a GHG and air pollutant. Ozone degrades crop output and human health [71, 169]. Because methane is an ozone precursor {via oxidation reaction: CH4 + 4O2 → CO + H2 + H2O + 2O3 [170]}, CH4 reduction would minimize ozone and ozone's allied ill outcomes. About 17% reduction of global methane emission per year is estimated to reduce ozone by ≈ 1 ppb, and radiative forcing by ≈ 0.12 W/m<sup>2</sup> [168]. Avoided global warming of such measures in 2050 is ≈ 0.28 ± 0.10°C [52]. Methane does arise from animal manure, municipal wastes, and landfills. Circular bioeconomy using AD as waste manager converts organic matter (energy crops/double-cropped biomasses, farm residues, animal manure, food processing wastes, space mission wastes, wastewater treatment plant effluent, organic fraction of municipal solid waste, and virtually any organic waste: whether previously sent to landfills or not), into valuable energy carriers (e.g., biogas and digestate). AD code would eliminate these ozone precursor sources, and their effects as environment-polluting wastes. As methane itself is a GHG of a global spatial scale, its reduction reduces its GHG effect; and combined with ozone & waste management, the benefits scale the entire world -all: human health, agriculture, ecosystems, countries, etc.

#### *9.1.5 Monetization, cost savings, and energy justice*

Circular bioeconomy could contribute to climate change mitigation by appealing to the morality, justice inkling, pocketbooks, and bottom lines of stakeholders. Profit margins and pecuniary savings might incentivize entrepreneurs/businesses to adopt circular bioeconomic tools. Studies monetized the benefits of climate mitigation via gains associated with O3 management [52, 168, 171]; and cost savings inherent in the application of digestate biofertilizer [102]. Monetized benefits of O3 reduction through NOx mitigation were estimated at \$1875 per metric ton of NO2, and that for NMVOCs at \$1100 per metric ton NMVOC [171]. For agriculture, forestry, and non-mortality human health, the estimate of global annual monetized benefits of O3 mitigation through 59 M ton CH4 reduction included \$7.8 billion avoided damages, and \$1.7 billion net cost savings at marginal cost of < \$81 per ton CH4 [168]. When human health mortality, crops, and climate were evaluated, monetized benefits of CH4 reduction as an ozone control measure were estimated at \$700 to \$5000/ metric ton CH4. This value was much higher than the usual marginal costs (< \$250/ metric ton CH4) required to implement abatement solutions [52]. Likewise, a study analyzed the economic implications of supplanting the inorganic fertilizer required for cassava root production with liquid fraction digestate. Results showed that about 25% of cost incurred in chemical fertilizer purchase could be saved with liquid fraction digestate. The monetized benefits were valued at \$0.141 billion for the year 2019 global cassava root output. However, this valuation was conservative as the monetization did not include external costs of inorganic fertilizers such as air pollution, eutrophication, GHGs, and the contamination of potable water supply reserves [102]. Related to profit motive is the ethical and philosophical inclinations of humans to do good albeit for self-preservation. Perhaps the moral allures of global energy access and security would prod policymakers to address issues of equity and justice in energy availability, accessibility, distribution, and affordability. Anaerobic digestion and biogas energy have been recognized to have the potential to achieve more sustainability and energy justice in society [100, 172].
