NOTE D - PATENT LICENSE FEES

Through a 2013 acquisition, the Company acquired certain patents, intellectual property and rights related to the development of Camelina as a biofuels feedstock, as a result of which it continues to incur costs related to patent license fees and patent applications for Camelina sativa plant improvements. These assets include three patents and the related intellectual property associated with these patents. These patents have an expected useful life of 17 years and are carried at cost less any accumulated amortization and any impairment losses. Amortization is calculated using the straight-line method over their remaining patent life. The termination of the patents are in 2029. Any future costs associated with the maintenance of these patents and patent and registration costs for any new patents that are essential to its business will be capitalized and amortized over the life of the patent once issued. The patent license assets as of the year ended December 31, 2019, 2018, 2017, 2016 and 2015 is shown in the following table:

Amortization expense for intangible assets was approximately $245,000 for the years ended December 31, 2015, 2016, 2017, 2018 and 2019. The estimated amortization expense for the next five years is expected to be approximately $245,000 annually.