The Internet of Things (IoT) is an important and growing research area in which physical objects such as transducers exchange data through communication networks to enhance system functionality. A crucial need for such devices is the provision of onboard energy resources. With the explosive number of IoT end devices being adopted, the effect of e-waste on the environment must be considered. One approach to address this issue is biodegradable energy sources for IoT devices, which can be utilized and disposed of in an environmentally friendly way. Zinc (Zn)-air battery chemistry, comprising a biodegradable Zn anode and an air cathode (normally comprising a gas diffusion layer and a catalyst layer) is a promising approach to these energy sources. In this dissertation, we developed Zn-air batteries from biodegradable materials and improved their performance considering the different power requirements of IoT end nodes, ranging from relatively high power microactuators to relatively low power active sensors. For IoT microactuators, high power and energy within a constrained space are required. Noting that the electrolyte of an electrochemical power source is typically the heaviest and largest component, the approach centered on the development of a lean hydrogel electrolyte based on potassium hydroxide (KOH). The high KOH loading and the addition of the additive potassium carbonate (K2CO3) improve battery output energy due to mitigating the loss of the hydroxide ion during discharge. The use of this hydrogel enables high device-level power density and energy density of the micro Zn-air batteries. Batteries were also scaled up to power a micromotor for a flying drone propellor, demonstrating a pathway for high-power Zn-air battery designs. For active sensors demanding a long operational lifetime, a scalable biowax encapsulation process was developed to protect the Zn-air battery. In particular, incorporating air management pathways for battery optimization was studied. The battery lifetime was further extended by researching neutral hydrogel electrolytes and biodegradable corrosion inhibitors. Integration with communication systems and agricultural field tests were then conducted to examine the performance of the batteries in a natural environment, demonstrating the potential of the biodegradable Zn-air battery as a long-term power supply for IoT sensors.