Dear Cindy,

As I understand, you are talking about the condensate I mean the volatile gases. During husk activation process you were utilizing the raw biomass that has huge amount of volatile. The gases were trying to escape from the pyrolysis reactor during the activation process but few amount of volatile either condensate on the wall of activated carbon or on reactor wall. Now we can designate that condensed gas with small amount of volatile solids as tar. This tar could be the orange color substance that you ask for.

There also would be an chance of few reaction byproduct formation during the activation of husk by H3PO4, but I really do not have any idea in this regard.

Now the question is how to overcome with this problem?

You can do something that help the volatile s' to escape from the pyrolysis reactor (or you can say we do not have to allow the gases to condensate in the pyrolysis reactor). You can reduced the size/length of volatile gases escaping duct/way during operating the reactor.  Small normal exhaust  fan may also be utilized to help the volatile gases to escape from the pyrolysis reactor. 

Hope this answer help you out to get few idea about you problem to solve them.

Regards,

Sandeep

For making biochar the temperature in excess of 400 C will lower the char yield and will cause the end product to very alkaline. Orange sludge may be iron oxide which becomes deposited under the alkaline environment. When condition are driven to very alkaline end product the iron will precipitate as an insoluble oxide which is often orange. If you collect the material and have it analyzed by atomic spectral analysis you can have a good idea of the atomic composition. When biochar is made not exceeding 400 C the material will not highly alkaline and can be used in neutral soils without liming the soil which through iron, manganese and zinc ppt gives micronutrient availability issues. 

Sodium Phosphate?

I think it is Tar.