It has long been recognized that composting yields a large quantity of thermal energy, which is normally lost to the surrounding environment as heat. Efforts to recover this heat using compost heat recovery systems (CHRSs) have been sporadic. Literature on the subject is also disjointed. To summarize the research that has been conducted, the authors performed an extensive literature review, covering publications in scientific journals, trade magazines, books, theses, and published reports. A focus on CHRS design and heat recovery rates is presented. The review covers 45 CHRSs in 16 different countries, ranging from simple hotbeds used in China 2000 years ago, to advanced super-thermal conductor heat pipe systems in 2016. Heat recovery rates varied significantly, with no predictable trend among the 45 systems. Recovery rates averaged 1895 kJ/hr (1159 kJ/kg DM) for lab-scale systems, 20,035 kJ/hr (4302 kJ/kg DM) for pilot-scale systems, and 204,907 kJ/hr (7084 kJ/kg DM) for commercial systems.

A comprehensive understanding of agroforestry adoption across a landscape is critical for effective agroforestry planning. The objectives of this study are to identify the sources of agroforestry data that can be used in the United States (U.S.) for national inventory purposes, discuss the possible uses and nuances of the datasets, synthesize the data to create regional maps, and provide recommendations for improving future agroforestry inventory efforts. To accomplish this, we queried multiple government databases containing agroforestry inventory data and spoke with agency representatives with in-depth knowledge of each dataset. Data from federal conservation programs were found to be useful for assessing practice-level adoption through a conservation program but not for general inventory use, since agroforestry systems can be established without federal assistance. For inventory purposes, the 2017 U.S. Census of Agriculture was found to be the most comprehensive dataset, with 30,853 farm operations reporting agroforestry use, representing 1.5% of all U.S. farms. However, this value is likely an underestimate, due to respondent unfamiliarity with agroforestry terminology. We propose several strategies to improve the accuracy of future agroforestry surveys, since a greater understanding of agroforestry adoption will influence decisions related to agricultural policies, technical assistance, and planning of these integrated systems.

Temperate agroforestry practices offer various ecological, social, and economic benefits. However, data surrounding drivers of adoption for agroforestry in the U.S. remains limited. A survey of Missouri agricultural land managers was conducted to determine the extent of agroforestry adoption in the state, current knowledge and perceptions of agroforestry, and interest in implementing agroforestry practices. A choice experiment model was employed to assess participants’ willingness to accept (WTA) payment for adopting agroforestry practices and to determine land managers’ valuation of technical assistance and environmental benefits. Across the sample, self-reported knowledge of agroforestry practices was minimal to low (33%-78%). Perceptions of agroforestry systems for management and economic aspects were mixed, while promotion of biodiversity and environmental services were especially positive. Using a mixed logit regression model, if cost to establish a given agroforestry system was $2,500 per acre, it was determined that the average Missouri land manager would accept a per acre payment of $8,795 for alley cropping, $1,217 for forest farming, $3,080 for riparian forest buffers, $-3,546 for silvopasture, $11,458 for urban food forests, and $19,154 for windbreaks. WTA payments were lower for existing adopters of agroforestry than non-adopters. Among those who were willing to adopt agroforestry, technical assistance was valued at $1,670 per acre, while environmental benefits were valued at $2,992 per acre. In a second model testing interaction variables, participants with greater knowledge of agroforestry practices or with higher incomes were significantly more willing to adopt agroforestry practices, while participants with larger farms were less likely to adopt agroforestry.

Agroforestry offers producers climate mitigation and adaptation benefits and the opportunity to diversify income and enhance ecosystem services. Though these benefits are well-researched, few studies document agroforestry implementation through time in the United States using consistent national data sources. To fill this knowledge gap, we investigated changes in the number of farm operations with agroforestry across the United States using data from the 2017 and 2022 United States Census of Agriculture. Through this analysis, we showed that the number of farm operations with agroforestry increased by 6% nationally between 2017 (30,853) and 2022 (32,717). States with the highest percent of total farms reporting at least one type of agroforestry were Vermont (7.8%), Maine (6.0%), and New Hampshire (5.6%), while states with the lowest percent were Arizona (0.3%), Utah (0.4%), and North Dakota (0.4%). States on the eastern half of the country tended to see increases in the number of farm operations with agroforestry between census years, while states on the western half of the country saw the largest decreases. Reasons for these changes are complex and require additional analysis. Additionally, we identified potential factors that may decrease the accuracy of agroforestry census data, along with recommendations on how to improve overall data quality going forward. We outlined how national agroforestry census data can inform decision-making related to farm policies, funding, programs, research, and extension delivery. With an online supplement, we also provided detailed maps of the extent of agroforestry in all 50 states.