**Preface to "Sustainable Agricultural, Biological, and Environmental Engineering Applications"**

Sustainable development in the agriculture sector is crucial to achieve the 2030 Sustainable Development Goals set by the United Nations. There are lots of challenges to developing modern and intelligent agricultural techniques, tools, and systems, by which sustainable agriculture and food security can be satisfied. In addition, carbon-neutral development and clean energy utilization are also associated with the UN-SDGs. Therefore, this book focuses on the recent proliferation and technological advancement in the agricultural, biological, and environmental engineering applications from the viewpoint of the agricultural water–energy–food security nexus. The book presents such engineering technologies and applications in seven categories that include: (i) energy system applications in agriculture, (ii) irrigation and drainage, (iii) biomass, biogas, and biochar, (iv) farm mechanization and soil science, (v) remote sensing and geographical studies, (vi) wastewater and biological studies, and (vii) case studies and societal aspects in agriculture.

In the category "Energy System Applications in Agriculture", three studies are reported. In this regard, an experimental study provides energy-efficient evaporative cooling systems for a poultry farm application. An air heat pump system is discussed for pig farms for sustainable energy efficiency, housing environment, and productivity traits. A CFD study offers a detailed inlet configurations analysis of the microclimate conditions of a novel agricultural greenhouse. The category "Irrigation and Drainage" provides four dedicated studies. An alternate design of a surface drain system is reported for the free discharge of subsurface drainage effluent. A sustainable irrigation system is discussed for small landholdings of the rainfed areas. An assessment of non-conventional irrigation water is conducted for greenhouse cucumber production. Soil erosion and sediment load management strategies are studied for sustainable irrigation in arid regions. The category "Biomass, Biogas, and Biochar" comprises three kinds of research findings. Regional biogas production potential from livestock manure is reviewed and explored. A low-cost biomass furnace development is explained for greenhouse heating. A study describes bioresource transformation to biochar and highlights its importance and potential applications for boosting the circular bioeconomy. Three studies are presented in the category "Farm Mechanization and Soil Science". A double-row pneumatic precision metering device is studied for Brassica Chinensis. The tractive performance of a single grouser shoe is investigated under different soil and moisture conditions. The effect of K and Zn application on the biometric and physiological parameters of different maize genotypes is explored. There are two research studies in the category "Remote Sensing and Geographical Studies". In this regard, the mapping of paddy rice with satellite remote sensing is reviewed. An estimation of regional maize straw resources is given using the Gaofen 6 satellite as the information source which has a high resolution and wide field of view imaging. Two studies are presented in the category "Wastewater and Biological Studies". A dedicated study explores the preparation and application of carbon nanotubes for water and wastewater treatment. One study reports that the compost inoculated with fungi from a mangrove habitat improved the growth and disease defense of vegetable plants. Five kinds of exclusive research studies are offered in the category "Case Studies and Societal Aspects in Agriculture". A state-of-the-art study from Iran presents the effects of the COVID-19 pandemic on food security and agriculture. A study presents the insights from Germany to address an interesting question, i.e., will farmers accept lower gross margins for the sustainable cultivation method of mixed cropping? Similarly, another study reports the empirical evidence from Polish farm households to address the question: Are farms located in less favored areas financially sustainable? A study from Pakistan predicts the behavioral intentions of rural inhabitants with regard to the economic incentive for deforestation. Another study from Pakistan assesses the contribution of citrus orchards to climate change mitigation through carbon sequestration.

The editors are pleased to share the above-mentioned seven categories comprised of emerging research and applications in the field of agricultural, biological, and environmental engineering. The editors believe that this book "*Sustainable Agricultural, Biological, and Environmental Engineering Applications*" will be useful for agricultural scientists, researchers, and students. The editors would like to acknowledge and thank the dedicated authors from each study for their valuable contributions to this book.
