instances of the trait EncodeBsonField are used to write key-value pairs to DBObjects. for instance, one of the provided definition in EncodeBsonFields is:
implicit val intEncodeField: EncodeBsonField[Int] = directWritable[Int]
you could use this like so:
val dbo = new BasicDBObject() //from the mongo-java-driver
implicitly[EncodeBsonField[Int]].writeTo(dbo, "someKey", 35)
athough, as the next section describes, there are easier ways.