A biodiesel may be prepared using an admixture of petroleum diesel and an algal derived hydrotreated renewable diesel which can be treated with petroleum diesel cold flow additives. The method includes providing sterilization wrap system with which to wrap the article to be sterilized. The amplified signals are constructively combined to form a pulse width modulation radio frequency signal comprising a plurality of non-negligible peak-to-peak amplitude levels each corresponding to a different baseband signal power range.