Nitrogen is an element. It is a gas forming about 80% of the air. Nitrogen is almost inert but it is a vital component in the proteins that go to making up living things. Therefore there is a natural Nitrogen cycle in nature. Nitrogen is trapped by bacteria forming the root nodules of certain plants (legumes and clovers) and during lightening strikes and is released back into the air by the processes of organic decay. Thus yes, the Nitrogen needed by living things is renewable.
Biomass can become a non-renewable source if harvested faster than plants can regrow. This can lead to deforestation and depletion of the resource.
A chair is not considered a renewable or nonrenewable source. It is a man-made product typically made from natural materials like wood or metal, which can be replenished by planting more trees or recycling metal.
electrical energy can be derived from a renewable or non renewable source. It itself cannot be classed as renewable as such because capacitors to store the energy are not 100% efficient in converting back to electrical energy
Geothermal energy is considered a renewable energy source because it relies on heat from the Earth's core, which is continuously produced. This heat can be harnessed to generate electricity and heat buildings without depleting the resource.
renewable