Unutilized Route Account

Quite often not all wood harvested from a block is sent to a mill. Some species may be surplus to the needs, especially in mixedwood stand types. This type of situation can be modelled in a Patchworks road network by using unutlized accounts. An unutilized account is essentially a 'fake' option to an exclusive account that is an alternative to sending products to a 'real' destination. Product values sent to an unutilized account are summarized, but road costs are not tallied.

For example, consider a forest with two mills: one takes only conifer and the other takes both conifer and deciduous. Conifer is in short supply, but there is a surplus of hardwood. If a mixedwood type block was harvested, the conifer could be sent to either mill, and the hardwood could be sent to the hardwood mill, or left in the bush as surplus. We can implement the surplus situation with an unutilized account, and let the model chose what wood to send to the hardwood mill and what to leave behind. Without the unutilized account, all hardwood would be forced to go to the hardwood mill, perhaps causing a very unrealistic situation. What we would expect in a rational situation is that hardwood products close to the hardwood mill will be utilized, and hardwood product further away will be declared surplus.

There is no specific 'unutilized' account type in Patchworks. The account is created by using an Exclusive Account to specify an alternative to the destination accounts. When Patchworks loads the model, it will create a summary account as a placeholder for the unutilized wood. When the scheduler runs the model will have an additional option about where to direct the products from a stand: to the real destination accounts in the route model or to the surplus account.

The following example illustrates how an unutilized account fits into the route model and how it is defined in the PIN file.

Figure 44. Unutilized surplus accounts


/*
 * PIN FILE
 */

control.addExclusiveAccount("product.Yield.Managed.Conif","destination.MILL1");
control.addExclusiveAccount("product.Yield.Managed.Conif","destination.MILL2");
control.addExclusiveAccount("product.Yield.Managed.Decid","destination.MILL1");
control.addExclusiveAccount("product.Yield.Managed.Decid","product.Unutilized.Decid");
	  

Unutilized accounts can be defined using exclusive accounts to simulate a surplus situation for some product types that may not be transported to a destination in the model.