One way to make use of the high number of old pallets is to upcycle them and turned into planters, which is what one of my favourite local cafes has done, creating a succulent and cacti planter.
Here they have turned the pallet upright and made a planter that holds a selection of succulents and cacti planted along each row.
A close up of some of the succulents and cacti in the pallet planter.
For instructions on how to make such a planter, this post on a Vertical Pallet Planter outlines how to do this.
But before you start, make sure you check whether the pallet you want to use has been chemically treated. If it has, you don't want to use it because the chemical used, methyl bromide (MB), is toxic. The DIY Projects site has a useful post on how to know if a pallet is safe to use.