**2. Environmental Impact of WWA**

#### *2.1. Air Pollution*

Energy extracted from burning the wood results in the formation of WWA. WWA is very fine, which results in the ease of pollution causing respiratory problems for human beings and animals around the site of WWA production [50]. Loose ash has a high possibility for harmful influence on ground vegetation [51], predominantly to the cover and certain kinds of moss groups [52].

#### *2.2. Land Pollution*

WWA is problematic if spread regularly and requires slow delivery rates from spreaders [51]. Because of the huge variety of WWA quality, reliance on the sort of chemical structure of WWA is needed before demonstrating the direction of management as agricultural or forest-related systems [53]. WWA recycling to agricultural or forests appears a decent environmental solution, but there are a lot of possible difficulties related to its use in systems, which are more multifaceted [51].

#### *2.3. pH Increase*

The topsoil of the system is affected by pH differences and its blocks the crop or tree to obtain enough amount of nutrition from the soil. The delivery rate of calcium to soils is reliant on the primary shape of the ash, with loose ash such as WWA possibly instigating a temporary quick increase in pH in the soil [54]. For the first 7 years, the soil under 100 mm depth had a very minor change in pH value after WWA application, but after 16 years, an increase in pH value was observed [51]. The land dumping of WWA results in the slow transfer of pH from the topsoil to bottom soil, which can be observed over time. There is an increase in the pH of runoff water over the same period where WWA is applied, as observed by Fransman et al. [55].
