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According to the Environmental Protection Department, the amount of green waste sent to landfills was 56,210 tonnes in 2013, i.e. 124 tonnes per day. This waste includes trees, leaves and some weeds, all of which are capable of decomposing naturally and therefore don’t need to be sent to a landfill.
In Australia, there are special sites to treat green waste within landfills. Loose components like leaves and weeds can be composted and sold to gardening companies as fertilizers. It takes around 3-5 months for green waste to decompose, the speed being largely dependent on the weather. The more bulky components like trees can be shredded into wood mulch. However, since the cost to send this to a landfill is too expensive, the private arbori-cultural company tends to do the shredding themselves and sell or give away the wood mulch to nearby residents.
According to my experience in Australia, a 340-square-metre garden requires about 1 truck load of green waste (8 tonnes) in 3 months. Our land is 3237.6 square metres and so can digest around 9.6 tonnes of green waste in 3 months, or 38.4 tonnes a year. The total size of active farmland in Hong Kong is around 729 hectares, which means 10,808 tons of green waste can be digested per year.
But what is the function of mulching? Firstly, it prevents sunlight from reaching the soil surface, which is beneficial for the soil to retain moisture and also control the growth of weeds. Secondly, when mulch decomposes, it provides valuable nutrients to the soil. Thirdly, it protects soil from erosion by rain. Lastly, mulch is significantly more attractive than regular soil. The soil in flower beds along the road in Hong Kong is always in terrible condition and looks awful.
As mulch is so useful, I am looking for a wood mulch source in Hong Kong, and I was looking even when I was still in Australia. However, I failed to find any and the reason is that there is no charge for the landfill. Dumping all the materials to the landfill is the cheapest and easiest way to treat all the green waste. If the arbori-cultural company really wants to do it in a more environmentally friendly way, they will need an extra truck to move the wood shredder to where the trees shall be cut and shred the wood on site. After that, they will need another extra truck to move the wood chips to the destination. There is another constraint to this in the form of Hong Kong’s narrow roads. They might not have the time and space to shred the wood on site. In that case, they will have to move all the materials back to the warehouse and shred the wood in the warehouse and send the wood chips to the destination. You can imagine how many extra costs this would incur. So, it is not even possible if you don’t mind paying for the wood chips.
Alright, I can’t find suppliers of wood chips. So, I shall make my own with my axes and loppers as my friends have suggested. We paved a road to the entrance of the farm with wood chips, of course not as fine as those produced by machines. Oh, I forgot to mention another function of wood mulch, which is to define where is the garden bed and where is the road, so people won’t step on our garden beds.
Author: Kelvin Kwok, a young farmer from Sheung Shui.